US2234727A - Method of applying liquid films in printing - Google Patents

Description

Patented Mar. 11, 1941 PATENT OFFICE METHOD OF APPLYING LIQUID FILMS IN PRINTING Philip A. Frazier, Oak Park, lll.

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Application May d, 1938,

aerial No. 206,401

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The invention relates to printing, and more particularly to letterpress or relief printing. More particularly the invention relates to the use oi liquid sprays which I have discovered are very beneficial in connection with the operation of printing presses. This application is a continuation in part of my copending application Ser. No, 171,521, filed October 28, 1937. In my copendingapplication Ser. No. 91,095, filed July 17, 1936, issued to Patent No. 2,127,955, August 23, 1938, I have described the use of a water spray on ink, which is particularly beneficial in promoting the transfer of ink to the surfaces to be printed upon.

The primary object of the present invention is the production of clearer, sharper printing even though the speed of the press is increased; the method of printing wherein the ink lies on the surface of the paper, producing an even color distribution; and an improved method of printing which will require from 10-30% less ink per job than in the customary methods, thus efiecting substantial savings. Printing ink is essentially a composition of pig-- ments of the required color mixed with oils or varnishes. In order to overcome their relatively slow rate of drying, depending upon polymerization, oxidation or absorption, drlers are usually added to the ink in order to increase the speed of the printing operation. These driers have the ability to accelerate the speed of the oxidation or polymerization of the oil or oil-varnish. Adifficulty presented with incorporating driers in the ink has been that the driers tend to oxidize or polymerize in the ink fountain or upon the ink rollers. An object of the present invention is to overcome this difficulty, and I have found that this objection may be eliminated by spraying driers upon the inking rollers or ink plate of the press in very finely divided form, thereby elimmating any tendency of the driers to congeal upon the printing rollers when the press is not in use and also enabling me to obtain a precise control of the amount of driers that can most suitably be added to the ink to meet the requirements of a particular job.

Printing inks are customarily manufactured and sold in various standard consistencies, and to meet the requirements of a particular job it is frequently necessary to thin or reduce the consistency of the standard inks. This is usually accomplished by adding reducers to the ink supply, either in the ink containers or the ink fountains, prior to printing. This practice is extremely (Cl. Mil-426) wasteful, in that it is irequently tound that the ink has been thinned too much and must be thrown away, and frequently, after the completion of a particular job, a considerable quantity of the ink is left over which is unsuited forum in" other jobs and must be reground. A further object of my invention is to eliminate this waste, and I have discovered that by spraying reducers, which may be in an aqueous suspension, emulsion, or solution, upon the components of the inking mechanism of a printing press, and that by varying the amount of the spray, very accurate control of the amount of the reducer can be obtained to obtain the exact consistency of ink required for any particular job. Accordingly, it is no longer necessary to mix compounds in the ink, with the danger of spoiling the job.

A further object of the invention is the provision of an improved method of printing which substantially eliminates picking, which is the tendency of ink to pull off a portion of the upper surface of the material to be printed upon.

A further object of the invention is the provision of a method of printing which practically doubles the printing life of composition rollers, thereby eil'ectlng a considerable saving in the time required to change and set rollers as well as a saving in the recoating or re molding of rollers.

A further feature of the invention is that it prevents the drying out of composition rollers and does away with the necessity of employing different types of rollers during thewinter and summer seasons. The invention has also been found very beneficial in keeping rubber rollers free from formation of ink cakes and in preservlng theircriginal tackiness.

It has been found particularly essential in the practice of the invention that in spraying any of the suspensions which I have found to be satisfactory, as will be hereinafter more fully described, on the rollers or ink bed of the printing structure, that the suspension or solution be in very finely divided form. An excess of the suspension in any spot or area is as objectionable as 5 is a deficit of the suspension. It also frequently occurs that the liquid accumulates in quantity on parts of the press where it is not desired and gets into the operating mechanism and may also drip onto the paper being printed. Many attempts 50 have been made to apply sprays of water onto the paper or to offset printing plates, and these have been unsuccessful because of undesirable accumulation of water in certain areas.

When water is divided into small globules,

these drops fall in absolutely quiet air, at a rate which depends upon their diameter and specific gravity. Drops of /2 millimeter in diameter, for example, will fall approximately 10 feet per second. Drops of mm. diameter will fall 1 foot per second, those of 50 microns 0& mm.) 3 inches per second, and those of 10 microns 1.2 inches per second. When their size is reduced below micron, the very fine particles do not fall at all in saturated air, but form a. colloidal suspension. The falling velocity of other liquids varies according to their specific gravities, but as most common liquids do not differ greatly from water in specific gravity, their falling rates are of the same order.

The air in the vicinity of printing presses in operation is always in movement, and therefore suspensions of small particles, which if left absolutely quiet would slowly settle out of the air, will in fact remain in suspension for a considerable time. A very moderate disturbance of the air will keep the proportion of liquid to air substantially uniform throughout, and any deposit of liquid from the suspension, under uniform conditions, takes place uniformly and gradually and can be accurately controlled. This characteristic is of great importance in connection with the successful operation of my invention. In sprays containing numerous particles of relatively large diameter, the heavy particles not only tend to deposit at a disproportionate rate, but it is impossible to maintain a uniform density of liquid in the air current, and irregular and uncontrollable results are obtained. It is preferred that the particles be kept below the size of approximately 50 microns, and it has been found that an air suspension of liquid of that order may be maintained in the neighborhood of the inking apparatus of a printing press in substantially uniform and homogeneous condition, and may also be regarded as a permanent suspension of liquid in the air. This degree of fineness is in fact of the same order as exists in a natural fog.

In order to obtain a suspension of liquid of the order described, I prefer to form the suspension mechanically, as by spraying, although fairly satisfactory results may be obtained by condensation of a vapor of the liquid. Highly satisfactory results have been obtained in employing the apparatus described and claimed in my applications Ser. No. 171,527, filed October 28, 1937 and Serial No. 221,092, filed July 25, 1938, but it is understood that other suitable apparatus is known to and available to those skilled in the art. It is not deemed necessary to repeat here the description of this apparatus, which is adapted to form particles of about 50 microns diameter. The heavier particles may be eliminated by a whirling motion of the spray within the nozzle or by passing the particles around a bend in the pipe. These particles, of course, may be produced in different types of apparatus, but it is of importance that. the projected spray be of a suspension of uniform density. As previously stated, the normal random movements of air around the inking mechanism of printing presses is suflicient to maintain this condition once it is obtained.

The rate of deposit from such a suspension may be very accurately controlled. When a stream of the suspension is directed against a surface, a portion of the suspended liquid will be thrown out of suspension by impact against the surface, and the rate of this deposit will be uniform and controllable by the velocity of the stream. The portion of the stream which does not impinge on an obstruction before it has lost its velocity (kinetic energy), however, does not tend to deposit liquid except by absorption or adsorption. This latter action, where it occurs, is gradual and comparatively slow and without any tendency to produce local accumulations.

In some cases it is desirable to promote absorption by surfaces which have an affinity for the liquid used, as for example paper for water, or composition printing rollers for water and glycerin. In such cases, an atmosphere of the suspension may be maintained around such surfaces, without velocity other than the normal movements of the air. In such cases the deposit is also uniform and controllable.

In the case of water sprays or suspensions, the particles which are not deposited eventually mix with the air of the room and evaporate, unless the air of the latter is already fully saturated, which is not ordinarily the case. In most cases the air of rooms in which printing is done is drier than is desirable, and humidification is often used to increase the moisture content of the air. The use of water suspensions as described therefore helps to create favorable printing conditions in the room, as well as performing a specific function in the printing operation.

The invention may be employed with any of the various types of printing ink, including the oil or varnish-base inks and the more modern cellulose base inks.

For particularly preserving and conditioning composition rollers, and also for facilitating the transfer of ink to the paper to be printed upon, the invention contemplates spraying the rollers with an aqueous solution of glycerine. Composition" rollers are widely used and are essentially comprised of a composition of glue and glycerine and frequently become heated in use and have to be removed and re-coated. The replacement and re-setting of the rolls involves considerable time when the presses are idle. By spraying an aqueous glycerine solution upon the rollers in particles of the very fine diameter and uniformity described, a thin film of glycerine is evenly deposited upon the rollers without the necessity of frequent scraping and manually coating the rollers. Furthermore, it is customary for every pressroom to have summer and winter rollers. The winter rollers have a larger glycerine content than the summer rollers. By the practice of my method I have found that the necessity for employing two sets of rollers is eliminated. I preferably employ a standard roller which has slightly greater glycerine content than a summer roller but less than the ordinary winter rollers. In the winter the rollers may be sprayed with a mixture of water and glycerine, which may be two fluid ounces of glycerine to one quart of water. In the summer the glycerine content of the solution to be sprayed upon the rollers may be reduced. This solution replaces-the moisture and glycerine lost by evaporation, due to the hot, dry atmosphere customary in printing establlshments during the winter months, and keeps the rollers from getting hard, hot, and from drying out. By this method I am able to satisfactorily employ an all-season roller which has less glycerine content than ordinary winter rollers, and it is not necessary to change the rollers with the seasons. I have found that, by employing my improved method, the normal life of composition rollers is practically doubled. The invention also has considerable utility with rubber rollers, in

distributor rollers or the form rollers.

that they. are kept free from having ink cakes formed thereon and are given the necessary tack to print well when sprayed with a glycerine or paraffin oil solution.

The spray may also comprise various thinners or reducers for ink in the form of very finelydivided particles, as previously described. It has been found that cottonseed oil, a solution of kero sene and water, paraffin oil and other solid oils from which excess grease has been removed, may be satisfactorily sprayed in the desired comminuted form and that by applying these solutions to the ink just before the ink is applied to the paper to be printed upon, and preferably while it is on the inking mechanism, that the consistency of the ink may be reduced as-desired by controlling the concentration of the solution being sprayed or the amount of solution sprayed. The spray is directed to the inking bed, the various rollers comprising the inking mechanism of the printing press, such as the ductor rollers, the

As previously described, the reducers are deposited upon the ink, whileit is in the inking mechanism, in the form of a fog which settles upon the ink slowly and uniformly in very small particles such as particles of 50 microns diameter or less. Clearly, if considerable portions of the thinner are deposited in a localized area on the rollers or inking bed, the consistency of the ink would be so materially reduced that it would lose its basic properties, and the resultant printing would be very spotty and of a poor unmerchantable quality. By applying the reducers in the form of a fog and accurately controlling the uniformity and rate of deposition, I have found that the consistency of ink desired for any particular printing job may be very accurately controlled. It will, of course, be understood that the concentration of the reducing solutions employed and the rate of deposition of the solution upon the ink in the inking mechanism of the press will vary, depending upon the original consistency of the ink and the requirements of the particular printing job. The ability to vary the consistency of the ink and determine the proper amount of reducer required for any particular job is within the knowledge of any experienced pressman.

Liquid driers may also be incorporated in the ink by applying the driers in the form of a very thin film to one or more parts of the distributor mechanism of a printing press, for example, to the ink bed, the distributor rollers, ductor rollers, form rollers and fountain. Numerous liquid ink driers have been found to be satisfactory when employed in accordance with my invention, for example, linseed oil, tung oil, poppy oil, preferably treated with litharge, or manganese sulphate, zinc sulphate, etc., in well-known manner, Japan driers or a solution formed as follows: The solution may comprise:

Linseel nil al 1 Lead oxide (litharge) --lbs 1% Acetate of lead (sugar of lead) lb drier may be applied to the ink just before it is applied to the paper to be printed upon. Highly satisfactory results have been obtained in the practice of my method, since there is no possibility of the driers polymerizing or settling out in the ink fountain, and, of even more importance, the ink will not dry upon the press while the press is being made ready. The spray of drier may be turned on after the first few sheets have been run, and I have found that a greater proportion of drier may be incorporated in the ink by my method than can be employed when the drier is mixed with the ink in the first instance. As a result, by the practice of my im-" proved method I am enabled to reduce the possibility of offset considerably, since the inks will dry faster on the paper printed upon. This is of considerable importance due to the present high speed operation of printing presses.

In practice, the various oils and greases, and the materials of an oily nature, all of which are not as fluid as water or miscible with water, may be comminuted into very fine particles by being forced into the line of a rapidly moving stream of air and Water under pressure, and the solutions of an oily nature will be carried in the spray in the form of an emulsion or suspension. The water portion of the spray, being non-miscible with most of the widely used printing inks of an oil or grease base, will be transferred to the paper to be printed upon while the oily portion of the spray, which may be a reducer or a drier, is readily miscible with, and will be absorbed by, the ink just before the ink is applied to the paper to be printed upon.

The invention further contemplates applying to the ink at the distributor mechanism of a printing press a liquid film of the nature described, comprising a mixture of a solution adapted to condition the rollers, for example, a solution of glycerine and water, and a material adapted to serve as a reducer or drier for the ink. It has been found that these materials may be satisfactorily applied to the distributor mechanism at the same time in apparatus described in my copending applications mentioned above. In

this apparatus the aqueous solution of glycerine is finely divided by means of an air blast, and the liquid drier or reducer is projected into the path of this liquid spray and is, in turn, finely divided and carried along with the spray under pressure to the distributor mechanism of the press where it is applied in the form of a fog.

The foregoing detailed description and specific examples have been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

Having thus described my invention and illustrated' its use, what I claim as new and desire to secure by Letters Patent is:

1. In letterpress printing, the method of incorporating in printing ink aqueous suspensions of an oily nature, comprising applying said suspensions in the form of a finely divided spray to said ink on the inking mechanism of a printing press while said press is in operation.

2. In letterpress printing, the method of treating printing inks during the printing operation, comprising selectively spraying a suspension, comprising liquids miscible and non-miscible with said printing ink, in the form of a finely divided spray upon the ink distributing mechanism of a press, while the press is in operation.

3. In letterpress printing, the method of incorporating in printing ink suspensions of an oily nature, comprising applying said suspensions in the form of a finely divided spray to the ink during the printing operation just prior to the time said ink is applied to the printing surface.

4. In letterpress printing, the method of printing which includes the step of applying to printing ink, just prior to the transfer of said ink to the printing surfaces, a suspension in the form of a finely divided spray, portions of said suspension being non-miscible with said printing ink, and the rest of said suspension being miscible with said ink, the non-miscible portion being transferred by the ink to the paper to be printed upon, and the miscible portion of said solution being incorporated in said ink.

5. In letterpress printing, the method of printing comprising spraying a liquid suspension upon the rollers of the ink distributing mechanism of a printing press during the printing operation, said suspension being in very finely divided form and comprising a substance adapted to condition said rollers of the inking mechanism and a substance adapted to reduce the consistency of said ink.

6. In letterpress printing, the method of printing comprising spraying a liquid suspension upon the rollers of the ink distributing mechanism of a printing press during the printing operation, said suspension being in very finely divided form and comprising a substance adapted to condition said rollers of the inking mechanism and a substance adapted to accelerate the drying of said ink after said ink has been applied to the surface to be printed upon.

7. In the letterpress printing art, the method of conditioning rollers of a printing press comprising spraying one or more of said rollers with a solution of water and glycerine in finely divided form during the printing operation.

8. In the letterpress printing art, the method of conditioning printing rollers composed of glue and glycerine, comprising continuously supplying one or more of said rollers with an aqueous solution of glycerine in finely divided form during the printing operation.

9. In letterpress printing, the method of applying liquid films to the distributing mechanism of a printing press, comprising spraying the rollers of said mechanism with a suspension in finely divided form oi. glycerine and a drying oil.

10. In letterpressprinting, the method of applying liquid films to the distributing mechanism of a printing press, comprisingspraying the rollers of said mechanism with a suspension in finely divided form of glycerine and an ink reducer.

11. In the letterpress printing art, the method of conditioning rubber printing rollers comprising continuously supplying one or more of said rollers with a suspension of paraflin oil in finely divided form during the printing operation.

12. In the printing art, the method of varying the consistency of printing ink during the printing operation; comprising spraying said ink, just prior to the time it is applied to the printing surface, with an ink reducer in the form of comminuted particles.

13. In the printing art, the method of reducing the consistency of printing ink during the printing operation, comprising applying to the ink, while it is on the ink distributing mechansm of a printing press, a film comprising very small particles of an ink reducer of the group of kerosene, paraflin oil and cottonseed oil.

14. In the printing art, the method of accelerating the drying of printing ink, comprising spraying said ink, while it is on the ink distributing mechanism of a printing press, with a solution of very small particles of a liquid ink drier.

15. In the printing art, the method of accelerating the drying of the printing ink after it has been applied to the material to be printed upon,

comprising applying to one or more parts of the ink distributing mechanism of a press a drying oil in the form of very finely divided particles.

PHILIP A. FRAZIER.