US391065A - Lithographic printing - Google Patents

Description

(No Model.) a Sheets-Sheet 2.

J., W. OSBORNE.

I LITHOGRAPHIC PRINTING.

No. 391,065 Patented 001;. 16, 1888.

(No Model.) 3 Sheets-Sheet a.

J. W. OSBORNE.

LITHOGRAPHIG PRINTING.

No. 391,065. Patented Oct. 16, 1888.

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UNITED STATES JOHN \V. OSBORNE, OF \VASHINGTON,

TO \VILLIAM H. FORBES, OF

PATENT OFFICE.

LITHOGRAPHIC PRINTING.

SPECIFICATION forming part of Letters Patent No. 391,065, dated October 16, 1888.

Serial No. 32.287.

(No model.)

To all whom it may concern:

Be it known that 1, JOHN \V. OSBORNE, of \Vashington, District of Columbia, have invented a new and useful Improvement in Lithographic Printing, of which the following is a specification.

My invention relates to the printing of all surfaces from which impressions are taken in the lithographic mannerthat is, by first [O damping said surface, then inking it, and, lastly, printing from it on paper, &c., by the application of pressure, and it has special reference to the first in this series of operations.

Hitherto the damping oflithographic stones and similar surfaces, as Zinc and photo-collographic plates, has been effected by a sponge, cloth, or by rollers. Thelatterare universally used in lithographic powerpresses at the present time, and in the following description I shall explain my method as it may be applied to the damping of a stone adjusted for printing in such a press.

The principle upon which my invention is based maybe thus stated. XVhen air saturated with water in the form of elastic vapor is. brought in contact with a colder substance, a part of the water so contained will be deposited on the surface of the colder body in the liquid form, as dew. This takes place because any lowering of the temperature of air which is saturated lessens its capacity for watery vapor and results in the precipitation of the difference between the quantities it can take up at the two temperatures. \Vhen the air is not saturated, moisture will still be de posited if the temperature of the colder body he at or below the dew-point-that is, cold enough to reduce the stratum of air in contact with it to a temperature just below that at which the amount of water present is sufficient for saturation. The first case is well illustrated by the film of condensed moisture produced when we breathe upon a plate of glass or of polished metal, which is colder than the saturated air issuing from the lungs; the second by the condensation of water as dew upon the glass and other objects out of doors when the same have been cooled to the dewpoint by radiation. The wcllknown appearance of moisture upon the outside of a vessel of ice-water when placed in a warm room is also a case of deposition from partly-saturated air.

To apply this principle to the damping of lithographic stones and similar surfaces,l carry to such a surface an atmosphere of air charged with vapor of water to the point of saturation or near it at a temperature above that of the stone to be damped. As a consequence the relatively cold surface becomes instantly covered with a film of condensed moisture. The amount of this deposit is influenced by the temperature at which the saturation was effected, by the difference between that and the tempera ture of the stone or other surface, the capacity 6 of the latter as a conductor of heat, and the volume of saturated air blown over the same.

In the drawings forming part of this specification, Figure 1 shows in plan part of a lithographic power-press with a stone upon the 0 reciprocating bed and the damping apparatus taking the position usually occupied by the damping-rollers. Fig. 2 is an elevation of the apparatus, looking toward the impression-cylinder,with parts of the press and the stone in section. Fig. 3 is an elevation of the apparatus as seen from the side of the press. Fig. 4 is a section through the saturating-box on a vertical plane passing through the ingress and egress openings and showing the perforated 8o termination of the stcampipe, 850. Fig. 5 is an elevation of part of the exit-tube conveying the saturated air, showing its relation to the pressframing and stone,on double the scale of the preceding figures. Fig. 6 is an elevation of part of the cxittube for compressed air, showing its relation to the press-framing and stone, on same scale. Fig. 7 is a crossscction of both the foregoing exit-tubes on line 00 00, Figs. 1 and 2, showing also the screen between them, on same scale. Fig. 8 shows in section the relative position of the several parts of the damping apparatus in a lithographic powerpress when double damping is used, small scale. Fig. 9 shows in longitudinal section 5 the way in which an induced current of air may be established by the force of the jet of steam used to saturate it. Fig. 10 shows an end elevation of thin elastic pieces of different size for attachment to the saturated air-exit IOO tube,on the large scale. Fig. 11 shows a plan View of three such pieces, same scale.

The tube 60 leads from a fan-blower or similar source of air at low pressure. It enters the closed saturating-box b,the escape from which is by the upright tube to the exit-tube d, which crosses the stone or other printing-surface as it reciprocates beneath it. The supply of air to the saturating-box is controlled by the valve e,and the discharges of saturated air upon the stone are determined by the cock f, worked automatically by a cam or other suit able device moving with the press, which opens and closes it at proper times. The quantity of saturated air which passes through the tube 0 every timef is opened is further controlled by the cock 9. \Vith this cock the workman brings the quantity of water furnished to the printing-surface down to a mini mum while the press is running without disturbing any of the other adjustments.

The saturation of the air with water-vapor is effected by the admission of steam at low pressure through the tube h, the intervals of ad mission being determined by automatic movements of the cock t, corresponding in time to those off, while the'gross quantity which can pass through the tube h is governed by the. cock It. The steam issuing in fine jets from the perforated sides of the pipe h, Fig. 4, meets the incoming current of air, raises the temperature of the same in proportion to its quantity,and passes as vapor at that temperature into the air,which thereby becomes saturated. These changes take place with great rapidity, and they are still further promoted if the air and steam be thoroughly mixed. The circumstances under which thetwo gasiform bodies enter the saturating-box are favor able to this mixing, and the partitions in the box I), asshown in Fig.4, render it still more perfect. The box I) and tube 0 should be covered with felt or othernon-conducting-material, (which is omitted in the drawings,) to prevent changes in their temperature due to external causes, and the whole apparatus should be blown through to warm it before it is used.

This is effected by opening the cock Z in the tube m, which leads to some waste-pipe, and all the other cocks except f. The relative quantities of air and steam are then so adjusted by c and k that the mercury in the thermometer n, the bulb of which is in the tube 0, rises to the temperature fixed upon and remains there stationary. Z and i are then closed, and the apparatus is ready for work.

Whenever in the automatic damping of the printing-surface the cocksf and t are opened, the air passing through 0 will have the constant temperature determined on, and will be practically saturated at that temperature as long as the air and steam are supplied at constant pressures.

The tube 0 leads from the saturating-box to some convenient place,where it is closed by a water seal sufficient to counterbalance the pressure of the incoming air through the tube ready egress.

ered by work.

a. I Its function is to remove any water blown into 0,01 which may be condensed therein, the quantity of which will always be small.

The saturating-box, with its connections, is herein shown and described as in close proximity to the press; but this is by no means a necessary arrangement, for it may be placed at a considerable distance-with equally good results, and often with advantage, if the tube a, bringing the saturated air, be well covered, so as to prevent it cooling, and thereby condensing the water-vapor before it reaches the stone. The tube d, at right angles to c,crosses the press above the stone and is closed at its farther end. On its under side, for the whole width of the stone, it is pierced with holes, through which the saturated air from c finds This tube is made of some nonconducting material-such as hard rubber and over the perforated part a fold of similar material descends on both sides to within a short distance of the stone. The two ends of this dependent chamber are closed, and the whole exit-tube so constructed (which the drawings will make intelligible) is attached to the tube 0 by the coupling p, and is also stiffened and supported b a rigid metallic bar, which is bolted at each efrd to the press-frame atq q. The small recessed grooves on the outside of this exit'tube along the. part nearest to the stone are for the reception of the turned-up edges of the thin pieces rrr. (See Figs. 10 and 11.) Several of these. pieces, made of very thin hard rubber, are providedof different widths. They are used, as required, to shorten the length of the open part of the exittube tosuit the varying sizes of stones, and

also (by employing those which are narrow) to modify locally on the stone the amount of precipitated moisture, decreasing it roughly in proportion as the printing-surface is cov- This they do by intercepting to some extent the downward flow of saturated air, which, nevertheless, finds its way round and under them, so as still to damp the stone, but in a lesser degree. These pieces are attached to the exit-tube when wanted simply by clasping them upon it and then sliding them into position, which position they then hold by virtue of their elasticity.

When one edge of the stone reaches the exit-tube d, the cocksf and i are thrown open, and they are closed again when the other edge leaves said tube. During this interval the saturated air (say at a temperature of 120 Fahrenheit) has been blowing down upon the cold surface, upon which a beautifully regular and perfect film of water is condensed. This disposition of dew is instantaneous and inevitable, because the least lowering of the temperature of the saturated air causes a sepa ration of the water, which, in consequence of the cooling it is subjected to at the printing It is not difficult to distribute the air very uniformly, and therefore the damping is uniform; but (due to their slightly-better conducting-power) the bare parts of the stone will receive more water than those places which are protected with ink, the repulsive power of the latter also tending to bring about the same result.

I believe myself to he the first to provide a method and means adapted for automatically delivering to those portions of the stone which bear no image a greater amount of water than to those portions which bear the image. The advantages, which are very great, lie, principally, in the fact that I am enabled in this manner to effectually dampen the stone, so as to prevent it from taking ink at points outside of the image without depositing upon the pertions which bear the ink so much water as to impair the quality of the ink. In the ordinary system of damping great difficulty is en countered in consequence of the water becom' ing mechanically incorporated with the ink.

Thequantity of water deposited will be influenced by the temperature at which the saturation is made, the coldness of the printingsurface as com'parcd to that temperature, and thevolume ofair blown overitduringitstransit under the exit-tube d. The first and last of these conditions, it will be seen, are completely under control; but the phenomena accompanying the precipitation of moisture are adverse for the maintenance of a wide difference in temperature between the printing-surface and the saturated air. This arises from the fact that it is impossible for that surface to cool the air and condense the water required to damp it without becoming warmer in consequence. The accession of heat, however, will be found to be very slight, because the damp ing by this method is so perfect that an exceedingly small amount of water is sufiicient. In cool weather it will cause no difficulty for a moment after each slight accession of heat is received. The inking-rollers from a cold inktable, with their heavy riders, act as most efficient cooling agents, as does also the cold sheet of paper on the impressioncylinder, which in the act of printing is pressed into intimate con.- tact with the whole surface of the stone. In other words, the little increments of heat imparted to the stone have not only to warm it cumulatively to an inconvenient temperature, but also to warm the inking rollers, their riders, the ink-table, and all the paper printed while the press is running. The warming of the stone due to the condensation of the water required for damping would, if considerable, prove inconvenient; but even then, as long as a difference in temperature is made to exist between the stone and the saturated air flowing over it, a deposition of water will take place.

In warm weather, when the printing-surface and all parts of the press have acquired the temperature of the air, it is expedient to cool the former, or at least to prevent an increase ofits heat. This may be accomplished in a variety of ways; but I prefer to use for that purpose air which has been compressed by mechanical means and cooled. The tube 8 leads from a receptacle into which air has been pumped until a considerable pressuresay fifty or sixty pounds to the square inchhas been reached. The heat evolved by this compression must be absorbed by a circulation of cold water, the evaporation of ammonia, or in other ways until the air in the receiver reaches the lowest temperature easily available, which is commonly that of the hydrant water on the premises. The details of this operation are well understood and need not be more fully described. The tubes leads to the exit-tube t, which crosses the press. The cook it controls the volume of air which can pass through the tube 8, and with it the workman regulates the degree to which he cools the stone while the press is running, and the cock 7) is opened and closed automatically by the press at the times when the exit of the compressed air is required. The exittuhet is made of some non-conducting substance, such as hard rubber, which answers .the purpose very well. It is attached to s by a coupling, and is closed at the farther end. All along its lowest part the tube t is pierced by a close row ofsmall holes, from which the compressed air issues downward upon the stone. This exit-tube is further stiffened and strengthened by a metallic bar, as in the case of the exittube for saturated air, which is bolted in like manner to the press-framing on each side. The position of this tube is par allel to that from which the saturated air flows and at a short distance behind it-that is, farther from the impression cylinder. The air issues from this tube very near the stone. At the moment of its escape it expands suddenly, and in doing so absorbs an immense quantity of heat, a large partof which it takes from the surface of the stone, which is cooled in eonsequence and its temperature kept at any desirable number of degrees below that of the saturated air, notwithstanding the heat due to the condensation of vapor which takes place upon it.

The cooling may take place while the stone is moving in both directions. The saturated air for damping I find it best to apply only when the stone is moving toward the inkingrollers, and the cams which move the cooks o andfare constructed and adjusted accordingly.

To prevent disturbance of the saturated air by the current of air under high pressure issuing from the tube t, it is well to interposc the shield or screw w, which is also made of non-conducting material. It is placed perpendicularly between the two exit-tubes, and its lower edge is as near the stone as may be. Its position should be such as not to interfere with the expansion of the air from t.

The employment ofnonconducting material for the construction of the two exit-tubes is recommended; but, though advantageous, its

use is not imperative, and many substances can be used as well as hard rubber. The ob ject aimed at is in the one case to hinder a cooling of the saturated air and in the other to hinder a warming of the expanding air before it is possible to print with an exceedingly small quantity of water, (a great desideraturn in lithographic printing;) but the quantity may be still further reduced by placing an exit-tube for saturated air on the other side of the impression cylinder beyond the inkingrollers. The relative position of the two exittubes is shown in Fig. 8. This can be done because of the very small space required for the damping apparatus. It is not then nec' essary to supply water in the first instance sufficient for a double rolling in with ink, for considerably less than half the usual quantity required applied from each exit-tube will b found sufficient.

In a reciprocating lithographic press a sin gle damping apparatus placed behind the im pressioncylinder, as is commonly done, damps the stone as it travels forward. WVhenthis is accomplished, the stone passes first under the ii'npression-cylinder without touching it, and then under the iuking'rollers, which successively traverse its surfaca After this the bed of the press has its direction of movement reversed, and the lithographic stone or surface with the design upon it returns. It passes first under the inking-rollers, then under the impressioncylinder bearing the sheet to be printed, the cylinder being urged downward, and finally to the damping apparatus, when all the foregoing operations are repeated. It will be seen that in such a press the quantity of water applied to the stone must be sufficient to keep its non-printing portion from taking ink while the stone is going forward under the inking-rollers, as well as during its return thereunder.

Recurring now to my method of damping, (shown in Fig. 8,) in which the total quantity of water is divided into two portions applied at different times, the following sequence of events is observed: As the stone in its forward movement passes under the exit-tube placed behind the impressioncylinder, the

saturated air is caused to flow out upon it in by letting the saturated air flow from the second exittube, placed in front of the rolls, as soon as the stone begins its backward move of the workman.

accomplished.

ment thereunder. In this way it will be perceived that the stone is damped preparatory to passing back under the inking-rolls to the impression-cylinder with a film of water just sufficient'to protectit during that short interval. In the ordinary system of inking all the water is applied at once for the complete inking, the quantity being far greater than that required for the first roll, so that it tends to impair the excellence of the ink, with whichit becomes incorporated to agr'eater or less extent. In my system I precipitate only enough waterfor each rolling upon the stone before "the rollers act thereon, in consequence of which the inking is done with a minimum amount ofwatera result highly advantageous in practice, in that it permits a clean impres sion and prevents the deterioration of theink. In the old system the inking-rollers nearest the impression cylinder receive the most water, and, being the last to leave the stone bekink at the finish, whereas in my system the terminal rollers are brought in contact with equal amounts of water, and the rollers which leave the stone last carry ink which has been damped by much less than half the total quantity of water. 7

Recurring to the method herein described for saturating the air with water-vapor, it should be stated that I am well aware there are many other ways in which a like result can be accomplished. It is, for instance, quite possible to use as a motiveforce for the saturated current the same jet of steam which supplies the moisture, for such ajet of steam discharged under pressure and blown into an open tube will draw a large quantity of air' .after it in the way shown in Fig. 9,which will be readily understood without further description; but in view of the several conditions to be fulfillednamely, temperature, force, and approximate saturation, and the wide range of each required to suit varying circumstances- I believe the method described to be the simplest and best, demanding, as it does,very little in the'way of nice adjustment on the part Likewise, I believe the construction and manner of applying the exittubes to be the best for the ends in view; but I do not confine myself to those forms and to that arrangement, as it is obvious-thatlboth may be modified without affecting the character ofmy invention or the principles involved. Furthermore, I am aware that the method herein described for cooling the stone or preventing its temperature rising in consequence of the condensation of water determined by it' is not the only way in which that end maybe It is possible, for instance, to use for that purpose a current of air which has passed over ice, or over a mixture of ice and'salt, &c., or to cool the stone by radiation to an artificially-cooled body in close proximity to it when it runs behind the impression cylinder, or two such bodies may be used, one before and one behind the impression-cylinder, or to cool the ink-table artificially, and so cool the stone indirectly, as well as in other ways; but Ibelieve that the method herein set forth, though I do not confine myself to it, is the most convenient and economical, and I have accordingly fully described it. It should also be stated that while from an abstractly theoretical point of' view the principles of my invention admit of perfect application under widely-varying conditions of temperature, the degree to which the stone must be cooled or the air warmed to secure sufficient and satisfactory damping is by no means a matter of indifference to the practical printer. If, forinstance, the lithographic stone were by the means described cooled down to some temperature near the freezingpoint, its surface would become coated with dew from the atmosphere, as it exists in most workshops, under which circumstances sufficient damping could undoubtedly be accom plished by blowing the ordinary air over the stone in sufficient quantity, obviating, apparently, the necessity for special apparatus to saturate it with the. vapor of water; or, to take the other extreme, the temperature of the stone might be allowed to' rise very high indeed, and still precipitate water if the temperature of saturation were correspondingly raised; but in either of these cases the printing qualities of the stone would probably be affected, and difficulties might arise which do not exist at present.

As far as the increase of temperature due to condensation is concerned, it may also be said that it remains the same for the same quantity of water restored to the liquid form Whether the saturation be made at a low or high temperature. It is quite possible, for example, to damp the stone very effectively with steam at 212. This would be an extreme case, one in which the proportion of air had finally vanished, and though a serviceable method under certain circumstances and in certain forms of press, and quite in accord with the principles of my invention, still it gives rise to difficulties, all of which need not be discussed in this specification. It may, however, be well to explain in reference to it that while the absorption of heat necessary to condense the water required for damping is no greater than ifthe same were condensed from saturated air at the temperature of the constant quantity of water so precipitated is in each case the same as that of the medium from which it is derived, (212 and 100 in the supposed cases.) To cool this water, however small it may be, adds another increment of heat to the stone, which leads to the general conclusion that the lower the temperature at which the saturation is effected the less will be the increase of temperature of the stone after each damping. If, on the other hand, the saturating temperature be too low, an inconveniently large volume of air will be required. In my experience temperatures varying from to according to circumstances, have proved most generally serviceable.

Under the term saturated air as used in this specification and in the claims I include not only air which has taken up the largest possible amount of water in the form of elas tic vapor, but also air which has approxi mately attained that condition, and generally air so charged with watery vapor at a temperature above that of the surface to be damped that in contact with such a surface it practicallyaccom plishes the end in view,even though in a strictly scientific sense it be imperfectly saturated. This explanation is desirable, because it may often prove convenient and economical in practice to employ imperfectly-saturated air and make up for deficiency in that respect by increasing the volume of such air conveyed to the printing -surface until the requisite quantity of water is obtained at each damping; and in this specification and in the claims, when reference is made to an atmosphere which contains the vapor of water, I Wish it to be understood that such an atmosphere may according to its temperature consist of such vapor in any proportion, increasing relatively to the air present from the small amount existing in the air we breathe (from which moisture will abundantly be precipitated if the printing-surface is sufiiciently cooled) to that in which, the temperature having reached 212, the vapor of water or steam, as it would then be called, becomes the sole atmosphere present to the exclusion ofair,for the condensation of such steam upon a cold surface, giving rise to a film of dew, is governed by laws precisely the same as those which determine the precipitation of asimilar film from saturated air at any temperature. In the latter case the air present plays no part as far as the quantity ofavailable water is concerned or the temperature at which condensation takes place and may be totally disregarded, the water-vapor filling the space occupied by the air exactly as if no air were present.

The advantages of the method I have invented for damping surfaces prepared for printing in the lithographic manner will be obvious to all persons conversant with the art. As compared with the usual damping method, it may be said that it obviates all the trouble and delay due to the management of the Waterfountain and the preservation of the rollers in an efficient condition. It damps the edges of the stone as well as the face. It can be applied both before and behind the impressioncylinder. The water used comes into existence as water of great purity only on the print ing-surface, the distribution and quantity of which are thoroughly under control, and the tendency of which is to accumulate on the places where there is no work. Finally, the water is applied without the contact of any solid body.

By the expressions surface and printing-surface as herein employed is meant a stone, metal, or equivalent body having its face adapted for printing in the lithographic manner, this being the sense in which the term surface is commonly used in the art of lithographic printing.

Having thus described my invention, what I claim, and wish to secure by Letters Patent, 1s-

1. The improvement in the art of printing in the lithographic manner, which consists in first exposing the printing-surface to an atmosphere containing the vapor of water, the dew-point temperature of which is higher than the temperature ofsaid snrface,and from which said surface obtains water by condensation, then inking the printing-surface so damped, and finally printing from the same on paper or other flexible material, substantially as and for the purpose described.

2. The improvement in the art of printing in the lithographic manner, which consists in first cooling the printing'snrface, then exposing it to an atmosphere containing the vapor of water, the dew-point temperature of which is higher than the temperature to which said surface has been cooled,and from which it obtains water by condensation, then inking the printing-surface so damped, and finally printing from the same on paper or other flexible material, substantially as and for the purpose described.

3. The improvement in the art of printing in the lithographic manner, which consists in first exposing the printing-surface to the'cooling effectsof expanding air, then to an atmosphere containing the vapor of'water, the dewpoint temperature of which is higher than the temperature to which said surface has been cooled, and from which it obtains water by condensation, then inking the printing-surface so damped, and finally printing from the same on paper or other flexible material, substantially as and for the purpose described.

4.. The improvement in the art of damping surfaces prepared for printing in the lithographic manner, which consists in first cooling the surface to be damped and then discharging upon it an atmosphere of the vapor of water or of air saturated with the vapor of water at a temperature above that to which said surface has been cooled, substantially as and for the purpose described.

5. The improvement in the art of damping graphic manner, which consists in locally adjusting the supply of water to the requirements of different parts of said printing-surface by interposing one or more obstructions, as r, in the descending flow of saturated air, which partially impedeihe same and hinder the access of water-vapor to said surface, substantially as and for the purpose described.

7. In a lithographic press, the combination of the impression cylinder, the stationary inking-rolls at one side of the same, the reciproeating bed or printing-surface, and two damping mechanisms, (1, located on opposite sides of the cylinder and inking mechanism, and each adapted, as described, to dampen the surface during its passage in both directions thereunder, whereby the damping of the stone is divided into four distinct operations, and thus the overdamping of the surface at any one time prevented.

JOHN W. OSBORNE.

\Vitnesses:

(3130. F. GRAHAM, JOHN SHERMAN.

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