US2078790A - Offset process - Google Patents

Description

. April 27,1937. EH, BUCY y:2,078,190

OFFSET PROCES S Filed Dec; 24,l 1951 Patented Apr. 27, 1937 PATENT oFFicE OFFSET PROCESS vEdmond H. Bucy, Waukegan, Ill., assignor, by mesne assignments, to Atlas Powder Company, Wilmington, Del., a corporation of Delaware Application December 24, 1931, Serial No. 582,919

10 Claims.

The present invention relates generally to the art of preventing offset upon freshly printed sheets.

When printed or lithographed sheets, as theyenierge from the press, are piled or super-posed one upon the other before the ink upon the sheets is dry, the contact of one sheet with the undry ink upon a freshly printed sheet tends to produce a condition that is commonly known as offset.

It, therefore, has been the practice in certain lines of printing or lithographing, where offsetting must be prevented, to spr-ay the sheets with an anti-offsetting medium as they emerge from the press. This medium is deposited upon the sheets in the form of minute particles which form, in effect, lands or projections upon the sheet, these lands serving to space the sheets apart sufliciently that the ink from one sheet will not be'transferred to contiguous sheets.

Heretofore, the anti-offsetting medium commonly employed has been a substance such as wax or paralne that could be liquefied by fusion and solidified by cooling, after application to the sheets. 'Ihe substance is in a solid state at room temperatures and is made uid by heat, such fluid being then sprayed upon the sheets by air or the like. The air serves to break up the uid into minute particles and these particles then solidify or regain their original solid state when depositedl upon the sheets.

I provide, according to the present invention, an anti-offsetting medium that is normally in a fluid state and which may be sprayed upon a `printed or lithographed sheet to form solid partilcles or lands for spacing the piled-up sheets apart sufficiently to prevent offsetting. This medium comprises, in the preferred form, a soluble material or solute carried in a suitable evaporable or volatilesolvent, In such solution there also' may be incorporated, if desired, any suitable plasticizers and any suitable inert llers or extenders which will serve to give atness or non-lighted upon the sheets. Sueh plasticizers or iillersv time Aor otherwise. Contra-distinguished from prior! anti-offsetting media the instant medium comprises a solution normally in a uid Y'st/ate. When the solution is sprayedv upon the sheets the solvent of the solution quickly evaporates. is evaporation occurs during the travel of the spray, as well as after striking the sheets, and hereby the solute or soluble material of the elution arrives upon the sheets in minute particles, which are sufficiently sticky or adherent reflecting character to the solid particles depositmay be applied separately, either at the same when they arrive upon the sheet, to remain and form, then or shortly thereafter, spacers of suflicient thickness to secure the desired result. Pref-" r erably the surface tension of the particles or droplets should begreat enough so that the particles retain, to a useful extent, the globular form, for the purpose of forming spacers of maximum height and minimum content.

The 4material may be applied by any of the known methods of spraying, i. e., pneumatic, mechanical or hydraulic, the object in each case being the formation and projection of a ne spray of particles of `a size great enough to provide the desired projections.

There are a number of advantages of my method, It may be carried out at less expense; it does not heat up the press room; the amountapplied may vary widely without objectionablel eiects; the material has much greater adhesive powers; it does not cloud the printed sheets nor render them greasy to the touch. As the, material which I apply sticks more firmly, the printed sheet is cleaner and more brilliant.

Other features and advantages of the invention will appear from the following detailed description when taken in connection with the accompanying drawing, in which Figure 1 is an isometric View of a portion of a printing press illustrating one method of applying my anti-offset medium to a printed sheet; and

Figure 2 is an enlarged fragmentary sectional view of two printed sheets illustrating the manner in which the solid minute particles or lands serve to space the sheets apart.

To practice the invention I provide a. solution in which the solute, preferably consisting of any one or more of the cellulose esters or ethers,.is carried in a suitable volatile solvent. These esters or ethers may, for example, consist of cellulose nitrate, cellulose acetate, ethyl cellulose or methyl cellulose, and are characterized by the fact that they are deposited from the solvent in a. tough film when the solvent evaporates. These cellulose esters or ethers, therefore, form the solid particles or. lands which are deposited upon the printed or lithographed sheet when the solvent evaporates. The solventin which the cellulose esters or ethers aiecaried pre erably consists, for example, of rapidly'evaporatigig solvents such as toluol, Xylol, alcohol, ethyl acetate, butyl acetate, cellosolve, acetone, ethyl lactate, carbon tetrachloride, or of any other solvents which have a relatively low boiling peint and vapor pressure, and thus will quickly evaporate, and will properly carry the cellulose esters or ethers in solution.

In order to give plasticity as Well as binding qualities to the particles or lands which are deposited upon the printed sheets, various plasticizers such, for example, as dibutyl phthalate, diethyl phthalate, tricresyl-phosphate, blown castor oil, camphor,' or any of the other plas ticizers which are suitable may be included in the solution, if desired. Also, inert fillers or extenders of organic soaps such as aluminum stearate, aluminum palmitate, or zinc stearate may, if desired, be included in the solution to give the requisite atness of surface or 'nonlight-reflecting characteristics to the particles or lands when they solidify. -In this connection, furtherinert fillers may also comprise such fillers as asbestine or dlatomaceous earth, fullers earth, magnesium carbonate, or any other material which would be suitable for such purpose. These materials may optionally be applied subsequent to the application of the particles of the solution and would be retained by the adhesive action of the droplets of the solution.

`It is contemplated employing any of the mechanical methods, such as any of the pressure, automatic or manually operable spraying mechanisms of well known types, for breaking up a solution of the above described ingredients into minute particles and spraying such particles upon the freshly printed sheets, or other sheets to be separated. To this end the solution of the above described ingredients will be prepared so,

as to have a consistency or viscosity that may best be handled by the spraying equipment employed, and capable of forming the desired spacing projections. The evaporated solvent may be carried away, as by exhaust fans or the like.

An example of one method of applying the above described solution to the printed or lithographed sheets is shown in Figure 1 of the drawing. In this figure, I represents a roll of paper to be printed and 2 the web of the paper. The web 2 is led between a printing machine 3 and the printed sheet then led over a sheet delivery reel 4. The spraying mechanism, designated generally at 5, is disposed in close proximity to the delivery reel 4 for spraying the solution onto the printed web 2.

` 'Ihis spraying mechanism comprises a plurality of atomizing nozzles 6 and 1 connected to supply pipes 8 and 9, respectively. The supply pipe 8 is in communication with a Suitable source of pressure, such as compressed air, (not shown herein) and the supply pipe 9 is in communication with a reservoir I0, which contains the antioffsetting solution. The nozzles 6 and 1 are so arranged with respect to each other that air from the nozzle 6 will comb across the nozzle 'l for spraying the solution onto the printed sheet.

The solution may be sprayed upon the printed sheet so as to form a continuous lm over the surface thereof, but preferably is sprayed upon the sheet to form a plurality of small raised particles or lands Ii. The volatile solvent of the solution begins to evaporate as soon as the broken up or-vaporized solution leaves the spraying device. The minute particles reach the printed sheet in a somewhat tacky and partially dry condition and dry completely immediately after striking the sheet. Their exposed surfaces are then suiciently hard and non-adhesive that they act as solid particles and will not stick to adjacent sheets. These small particles, or lands, rise above the surface of the f l'eShly Printed Sheet 2 (Figure 2) and form lands or barriers Il for spacing the sheet i2 out of intimate contact with the sheet 2, to prevent offsetting.

The consistency of the solution is about the same as now used for lacquer spraying and preferably slightly thicker. However, care must be taken not to let the spray become thick enough to merge the drops on the surface of the printed sheets.

The solution may be applied to the printed sheets by one or more spray guns. These spray guns may consist of hand operated guns, automatic machines, or of any other suitable device for breaking Aup the solution and ldepositing it upon the printed sheets.

While I have illustrated, by way of example, one method of applying my anti-offsetting solution to a printed sheet, it is to be understood that I do not intend to limit myself to the use of such a method, as the essence of the present invention resides primarily in the provision of an antioisetting medium which, when sprayed in any suitable or preferred manner, will deposit minute particles upon a freshly printed sheet by the evaporation of a volatile solvent. apparent that soluble solids, other than those above mentioned, may be employed, as well as a complete range of other solvents, plasticizers It will also be and inert fillers, without departing from the spirit of the present invention.

What I claim is: I

1. The method of holding sheets of paper out of too intimate contact which consists of forming a plurality of spaced projections upon the surface of one sheet by spraying it with a solution comprising a. solid dissolved in an evaporable solvent of low boiling point and vapor pressure.

2. The method of holding sheets of paper apart which consists of forming a plurality of solid individual particles on one of the adjacent surfaces by spraying it with a solution comprising a solid dissolved in an evaporable solvent, the solvent being adapted to evaporate substantially entirely in the time of travel of the spray to the sheets.

3. 'I'he method of preventing offsetting of printed sheets which consists of forming a plurality of minute disconnected particles upon the surface of the sheets by sprayingthem with a solution of a cellulosic material dissolved ina volatile solvent, the solvent substantially entirely evaporating in the time of travel ofthe spray to the sheets, and the cellulosic material reaching the sheets in a tacky and adhesive condition.

4. 'I'he method of preventing ink offset which consists in producing 'on a newly printed sheet a non-coherent spacing layer of particles from a material comprising a substantially colorless body substance and a volatile carrier.

5. The method of preventing ink offset in printing or like operations which consists in creating a finely divided mist-like stream of fluid material embodying a solid component and a volatile constituent, and directing such stream toward a surface of a newly printed sheet from such a distance as will effect substantially a complete removal of said volatile constituents during the passage of the stream through said distance leaving only minute particles of the solid component to be impacted against said surface.

6. The method of spraying a printed sheet to prevent offset which comprises passing said sheet past a given point, producing a finely divided spray of an evaporable solvent and a body member, and directing said spray upon said sheet as it moves past said point from a distance such that said evaporable solvent is substantially volatilized and substantially dry particles of said body member are produced at approximately the moment of impact against said sheet.

'7. The method of preventing ink oifset which consists in directing toward a newly printed sheet a'spray produced from a material containing a solid substance dissolved or suspended in a volatile liquid, said spray being formed of such iinely divided particles of material that during passage thereof toward said sheet the liquid volatilizes suiiiciently to produce a deposit of substantially solid particles on said sheet. 8. The method ot preventing ink oiset which includes the steps fof creating a spray from a fluid material containing a particle forming substance and a carrying medium capable of evaporation, directing said spray toward a sheet to be treated, and allowing the carrying medium to separate from the particle forming substance as the spray passes from its point of creation to the sheet whereby substantially solid particles are depositedupon said sheet.

9. The method of preventing ink offset which includes the steps of evolving a spray from a v uid material which in composition is characterized by the production of a residual substantially solid substance upon evaporation o! a iluid component, and directing said spray toward the su.r face of a newly printed sheet, during which passage sumcient evaporation of said iluid compo- Y nent occurs todeposit on said surface particles of said substance in substantially solid form, said substance having properties which permit subsequent printing operations to be performed upon a treated sheet.

10. The method of preventing. ink offset in" 'printing or like operations which consists in creating a finely divided mlstlike stream of uid stituent through volatililzation and produce sub-A stantially dry particles of said solid component at approximately the moment of impact against said surface. ED. H. BUCY.

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