US299002A - Method of and apparatus for damping lithographic surfaces - Google Patents

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(No Model.) 2 SheetsSheet 1.

J. W. OSBORNE. METHOD OF AND APPARATUS FOR DAMPING LITHOGRAPHIG SURFACES.

No. 299,002. Patented May 20, 1.884. .1 22- N. PETERS. PhnQo-L'nhugnpher. wmmmm. D c.

(No Model?) 2 Sheets-Sheet 2. J. W. OSBORNE. METHOD OF AND APPARATUS FOR DAMPING LITHOGRAP HIO SURFACES.

No. 299,002. Patented May 20, 1884;.

I 9 i o five/7227: Wfi/wssfis: I O x v N. PETERS. Phalniithogmpher. Washmgmn. D. c.

Warren Ermine Parmvr tribe.

, JOHN \V. OSBORNE, OF \VASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO IVILLIAM H. FORBES, OF BOSTON, MASSACHUSETTS.

METHOD OF AND APPARATUS FOR DAMPING LITHOGRAPHIC SURFACES.

SPECIFICATION forming part of Letters Patent No. 299,002, dated May 20, 1884.

Application filed June 18, 1881.

To OJZZ whom it may concern.-

Be it known that I, JOHN W. OSBORNE, of Washington, District of Columbia, have i11- vented a new and useful Improvement in the Method of and Apparatus for Damping Lithographic Surfaces, of which the following is a specification.

My invention is related to the methods employed for damping lithographic stones and to the devices in use for performing that opertion on all-surfaces which are printed from in a similar way; and it is especially valuable when such printing is done in a power-press. As one of the steps in the process of printing from lithographic stones or zinc plates, or from collographic surfaces prepared photographically or otherwise, it is necessary to damp with water the non-printing parts 011 which there is no design, so as to prevent, adhesion of the ink to thesame when the inking-rollers are applied to such surfaces. In power-press printing this operation is usually accomplished by damping-rollers in stationary bearings, under which the stone passes. These rollers are constructed of absorbent material, and are fed with water by a carrying-roller from a suitable fountain. This damping apparatus occupies considerable space, and to maintain it in perfect working order is difficultl The rollers are liable to wear and harden, and they have to be frequently cleaned, covered, and otherwise repaired. Even when acting in the best manner their friction and wearing action upon the printing-surface are an evil which cannot be avoided. Instead of applying the necessary water by the intervention of one or more moistened rollers, it is, when my invention is used, projected upon the printing-surface in the form of a cloud of finely-divided particles without the contact of any solid body. This atomization of the water I effect by mixing cooled air with steam, or with air saturated with the vapor of water, in quantity sufficient to condense the latter, whereby a mist consisting of very minute and uniform water globules is produced. For this purpose the air may be cooled in a variety of ways well understood in the arts-as, for instance, by exposing it to v the cooling action of a freezing mixture, or to the cold produced by the evaporation of volatile bodiesbut I prefer to accomplish it by (N0 model.)

first compressing the air which is to be used by means of a pump, and then absorbing the heat generated by the compression by a circulation of water in the well-known manner. The air so compressed and cooled to ordinary temperatures is allowed to expand in contact with the water-vapor. In doing this it falls immensely in temperature, (the fall bearing a constant relation to the degree of compression applied,) and as a consequence causes a condensation of the vapor to water by robbing it of its latent heat. The condensed water, by this method, inasmuch asit is produced simultaneously in all parts of the mixture, is in the form of a cloud of very great uniformity, and if the operation be conducted within an inclosed space, not only is it easy to give the cloud an equal density throughout, but the degree of density is also very thoroughly under control. The production of cold air by expansion is very convenient, because by modifying the extent to which the compression has been carried, (a change easily made,) a greater or less amount of such air will be required to eifect condensation of a given quantity of steam, for it is plain that the quantity of cold air required will in all cases become less and less as its temperature descends. below the dew-point, while the density of the cloud of So atomized water will increase in the same ratio.

The drawings accompanying this specification, and forming part of the same, illustrate some of the ways in which my invention may be applied.

Figure 1 shows in plan a portion of a lithographic power-press with a stone in position under the damping apparatus, in which the atomization takes place directly over the printing-surface. Fig. 2 is an elevation of the 0 same, looking toward the impression-cylinder, (not shown,) with portions of the press in section. Fig. 3 is an elevation of the same seen from the side of the press. Fig. 4 is a crosssection of the atomizer 011 the line 1 1, drawn 9 5 on three times the scale of the preceding. Fig. 5 shows in plan a portion of a similar press, in which the atomization is effected at a distance from. the printing-surface. Fig. 6 is an elevation of the same looking toward the im- 10o pression-cylinder. Fig. '7 is an elevation of the same as seen from the side of the press.

, non-conductor of heat, as hard rubber.

Fig. 8 is an elevation of the atomizer used "111 the preceding on three times the scale. Fig. 9 is a cross-section of the same on line 2 2.

In Figs. 1, 2, 3, and 4, a represents a lithographic stone on. the bed of a reciprocating press. A tube, 1), of small diameter, conveying steam, rises at the side of the press to the level of the printing-surface, and is closed by the cock 0. A similar tube, (2, rising parallel to 1), leads from a reservoir, in which air has been compressed and cooled. This tube is closed by the cock 6. Across the press, in thepositiou usually occupied by the dampingrollers, and at a short distance above the stone, the atomizer is placed. It consists of two tubes, f and closed at one end, but communicating, respectively, with b and d by joints which are easily made and broken, and also with the shallow mixing-chamber h, which has no bottom, bynumerous perforations opening into the latter. It is best to construct the tubes fand g of some substance which is a The atomizer is further stiffened by the bar of metal i, to which the tubes and chamber are at tached, and the ends of the bar are bolted to suitable supports on the framing of the press.

The management ofthis apparatus for damping is exceedingly simple. The cocks c and c are moved automatically by connecting them with suitable cams or similar devices operated by the press. When the edge of the printing-surface reaches the mixing-chamber 72, both cocks are thrown wide open, and when the other edge leaves it they are closed. The quantity of water which shall reach the stone during its transit under the atomizer depends primarily upon the quantity of steam passing through I), to condense which adefinite proportion of compressed air passing through dis required. These relative amounts are adjusted by closing the cooks 7c and Z (on b and (1, respectively,) to a greater or less extent, eachof which when fully open lets more pass than is wanted under any circumstances. WVith steam and air at constant pressures, the positions of k and I bear a recognizable relation to each other, which can be ascertained and modified with great facility by the divided segments attached to them. When the two gaseous bodies in proper quantities meet in the mixing-chamber h, (the precise form of which is subject to modification,) the volume of steam is instantly annihilated, and in its stead water, occupying one seventeen-hundredth of its bulk, remains suspended in the expanded air, which is projected forcibly against the stone; or, to state it differently, every cubic foot of steam which enters the chamber of the condensing-atomizer will instantly give rise to a cubic inch of water. An excess of condensed air in this operation produces no other effect than to reduce the density of the cloud of atomized water and to lower its temperature, and therefore, by gradually closing the cock k on the steam-pipe b after the press has started, the quantityof water deposited on the stone (4 may be reduced to a minimum, after which unnecessary air may be cut off by closing Z.

In an application for patent filed in theUnited States Patent Office by W. H; Forbes and J. W. Osborne, on the 20th day of April, 1881, No. 31,287, a method is described for damping surfaces prepared for printing in the lithographic manner, by depositing water thereupon in an atomized condition, said atomization being accomplished at a distance from the surface to be damped and by means purely mechanical. The invention herein set forth may also be advantageously applied for'like purpose in an arrangement of apparatus es sentially similar.

In Figs. 5, 6, and 7, m is alithographic stone in position as before. a is a horizontal tube or trunk closed permanently at one end, and at the other provided with an adjustable valve, 0, which may be conveniently constructed in the ventilator form. The trunk or mixing chamber at is open at its under side for the whole width of the stone, and is supported a little above the latter by attachments to the framing of the press. mizer is placed in this-trunk just inside the valve 0, and-it may have various forms calculated to promote the rapid and thorough mixing of the steam and expanding air in proper quantities. This is very well accomplished by the construction shown in Figs. 8 and 9. It consists of two hollow rings, p and g, which communicate, respectively, with the tubes 1' and s, the former of which furnishes steam and the latter compressed air. The rings are placed parallel to each other, the smaller one being slightly behind. Both are perforated with a number of little holes. These are so located that while the j ets of steam are directed radially inward, the current of expanding air is directed forward. The cloud of atomized water formed under these circumstances is carried through the trunk and blown down upon the printing-surface, thereby effecting the damping. The tube tconducts away from the trunk any moisture collected from its inner surfaces in the manner explained in the application above cited. The cocks at and c on the tubes 1" and s, respectively, are opened and closed by the-action of the press at proper times. The cocks w and w adjust the quantities of air and steam supplied. The advantages gained by this method of atomization over mechani-- cal ways of doing the same in an apparatus of the kind shown are due chiefly to the fact that no relatively large drops are formed, so that all the subdivided water may be used and also to the exceeding minuteness of all the particles,which can therefore be carried a long distance with a feeble current of air and evenly distributed over a large surface. In the arrangement shown the cloud may be carby the force of the expanding air supplied in sufficient quantity; or, if it is desirable to The condensing atoried forward over the printing-surface simply economize that, by the force of an induced current entering at the valve 0. In the former case the valve 0 must be closed, and the quantity of compressed air increased, if necessary, till the requisite force is obtained, such increase being, of course, accompanied by a fall in temperature. In thelatter it is opened wide enough to let the outside air enter as a slow voluminous stream, induced by the intense local current from the atomizer, and carry the cloud forward to the printing-surface, the tempera ture remaining in this case unchanged.

In the forms of apparatus for damping surfaces printing lithographically, described in the foregoing, the atomization has been effected by a mixture of steam with cold air; but, as has been already said, air saturated with the vapor of water or heavily charged with the same may be substituted for the steam with similar results and without departure from the principle on which my invention is based. In such cases the proportion of air accompanying the vapor, be it much or little, has to be cooled also, which is an unproductive demand upon the cold air supplied. The higher the temperature at which the saturation has been effected the larger will be the quantity of water condensed by a uniform volume of cold air, because in the process of saturation, however it may be done, as the temperature is.raised the air takes up a continually-increasing quantity of water-vapor until at 212 Fahrenheit, and under ordinary atmospheric pressure water only, in the gaseous form, may constitute the whole to the exclusion of air. Whether steam or humid air be used, the density of the cloud produced will depend upon the relative quantities of water-vapor and air cold enough to condense it, which meet and mix within the space in which the atomization takes place. The larger the quantity of water-vapor forced into such a space and the smaller the quantity of air necessary to take up its latent heat, or, which is the same thing, the greater the pressure by which that air was compressed before cooling it the denser will be the cloud of atomized water produced. This density can be further increased by using steam under pressure. The heat above 212 which such steam must necessarily possess, will not require any cold air for its absorption, for. the high-pressure steam at the instant of its escape and expansion will of itself fall to 212. By using it a larger quantity of water-vapor in a given time is brought in contact with the cold air; but the same weight of vapor condensed to the liquid form will require the same quantity of cold air whether the temperature of the former be 212 or far higher. It will be understood from the foregoing explanation that this method of atomization, as I apply it for damping purposes, can be controlled and modified in a variety of ways, and that by it a very small inclosed space can be filled with a uniform and perfectly-atomized cloud, which it is difficult if not impossible to accomplish by purely mechanical means.

Having thus described my inventiomwhat I claim, and desire to secure by Letters Patent, 1s

1. The improvement in the art of damping surfaces prepared for printing in the lithographic manner, which consists in mixing the vapor of water, or air saturated with the vapor of water, withair which has been cooled, for the formation of a cloud of condensed and suspended water particles, and then depositing said particles of atomized water upon the surface to be damped.

2. The improvement in the art of damping surfaces prepared for printing in the lithographic manner, which consists in mixing the vapor of water, or air saturated with the vapor of water, with air which has been compressed, cooled to ordinary temperature, and then released from pressure, for the formation of a cloud of condensed and suspended water particles, and then depositing said particles of atomized water upon the printing-surface.

3. That improvement in the art of damping surfaces prepared for printing in the lithographic manner, which consists in bringing simultaneously upon the surface of a lithographic stone or its described equivalent, and upon the same part of it, water in the form of vapor at any temperature and air sufficiently below the dew-point of said vapor to effect the condensation and conversion of the same into a cloud of water particles, which latter by their propulsion against and attachment to the printing-surface accomplish its damping, substantially as and for the purpose de scribed.

4. The combination, substantially as described, of a condensing-atomizer, with means, substantially as described, for controlling, directing, and circumscribing the quantity, movement, and distribution of the generated cloud of atomized water over a surface pre pared for printing in the lithographic manner, and with a lithographic press, substantially as and for the purpose described.

In an apparatus for damping printingsurfaces by projecting atomized water against the same, two tubes provided with adjacent terminal openings, and communicating the one with a steam'generator and the other with a reservoir furnishing compressed air at ordinary temperatures, substantially as and for the purpose described.

6. In an apparatus for damping printingsurfaces by projecting atomized water against the same, a mixing-chamber opening upon a lithographic stone or its described equivalent, and furnished with orifices for entering jets of steam, and for air cooled by expansion or otherwise, in combination with said printingsurface, substantially as and for the purpose described.

JOHN T. OSBORNE.

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