US1742618A - Overlay sheet and method of producing the same - Google Patents

Description

Jan; 7, 1930. s n- 1,742,618

OVERLAY SHEET AND MET HOD OF PRODUCING THE SAME 'Filed Jan. 17, 1929 Patented Jan. 7, 1930 UNITED STATES PATENT OFFICE ARTHUR L. sHITH, on BosToiv, MAssAcHusETTs, PORATION, or CAMBRIDGE, MASSACHUSETTS, A

OVERLAY SHEET AND METHQD or rnonuomo THE sun CORPORATION or mssAcHUsn Ts Application filed J'anuary'17, 1929. Serial No. 333,115.

This invention relatesto overlay sheets which are usually employed on the cylinders or platens of printing presses beneath a tyn1-' pan, for the purpose, primarily,

of'i'mprov-ing the results secured by the printing operation from half-tone cuts, the preparation and adjustment of such sheets being an operation known as make ready. a

M are particularly the invention relates to that type of overlay sheets in which a ow-f dered material is placed on a freshly'p r nted proof sheet, so that'a. portion of the material will be -retainedby,the wet ink when the surplus material'is shaken oii the sheet, a .-further operationusually being necessary to attach the material-to the sheet which was re-' tained by the ink, so, that certain portions of the sheet become permanently embossed.

The above type of sheet is to be distin guished from those types in which portions 7 of the sheet are actually out out, or built up by pasting on which the' proo is printed on specially 'pre pared paper, which later is etched in a suitable bath. Overlay sheets made by thecut out method are expensiveand often require a high degree of skill in their preparation,

- but both methods are disadvantageous in certain respects, for various reasons, one of the principal of which is the length of time required to make the sheets, for the time required to makean overlay sheet is often a ly 1n proportion to'the depth ofthe shadowsmuch more important consideration than the labor cost of making it, as the press on which the overlay sheet is to be used-must beidle While the sheet is being prepared, and there is often a'demand that the printing operation to (performed as quickly as possible.

ne of the principal defects in the embossed overlay sheets, made by processes which have been previously employed, is due to the fact that the extent of the embossment of any portion usually fails to be even approximatein the picture to be reproduced, so that, when the picture is printed, the desired gradation of the difi'erent tones are not secured. -Another defect is due to the use of various adhesive and liquid coatings to secure embossing material to the sheet, which are likely to iecesof paper, orthose in, i likely to be caused to a found to be process 0 cause; expansion orcont-raction of the sheet as a whole, so that it becomes practically impossible toposition fthe, overlay sheet in .correct relation to the printing characters. Ad

hesives arealso usually ineffective in securing the embossm'ent to the sheet, so that the em- I AssIGnoRfTo camno OVERLAY core a bossment has been coated with shellac, silicate ofsoda and other self hardening adhesives to secure it, and where the overlayis coated with such materials, a hard, brittle, and somewhat glassysurface is usually produced thereinder on the bed-tends to crush the embossment, so as to destroy it, or reduce its effectivectionable-for several reasons, some of which are that the pressure ofthe' cylness to such an extent that the sheet becomes .practically useless after it has been used for a-short portionof the-desired run,

also, such a sheet is liable to slip sli htly out'of position on. the cylinder, and,i a sheet slips even slightly, the printed results are not only like or type.

The objects ofmy invention are to produce anoverla sheet of the embossed type and a positionof substances to. beemployed in the production. thereof, which-will obviate many of the objections-to overlay sheets of this type, particularly by producing sheets which will be as heavily embossed on the low lights,

making thesame including a comor solid tones, as may be necessary to produce solid black, or other solid color on the corresponding parts of the matter to be reproduced, and which will be less heavily embossed on tliemiddle and grey tones, so that the desired gradation ofshade will be secured on these portionsof the printed reproduction,

and which will be. entirely un'embossedon the high light portions, so that they will not a be inked at all in printing and the'pressure.

on these portions of a plate or cutwill not be increased.

Also to provide 'a process which will make it unnecessary to use -a special ink in striking off the proof, and will permit the use of .anyink which happens to ,be*su@fied to the press. i

Other objects are to provide a process of producinganimbossed overlay sheet which will not necessitate the use of any material i in liquid form, but will permit the sheet to be kept dry throughout the process, so that there will be no action tending to cause the sheet as a whole to expand or shrink. Also to provide a process which will merely necessitate heat ing the sheet to fix the embossment thereto and which, on" fusion of the material, will nevertheless prevent liquid of fusion from flowing over the lines between the different shades, so as to cause distortion of these lines,

- p and will also cause the edges of the more heavily embossed portions to be beveled, so that the increased pressure secured by such portions will notincrease thepressure on adj acent portions.

Also to produce an embossed overlay sheet V which will normally have a somewhat roughened, pebbly, or corrugated surface, but which is also resilient, so that it may be pressed. flat while under'the direct pressure of the cylinder, but will resume its pebbly surface when the pressure is removed, and which will normally frictionally engage the tympan, by

causing slight'indentations therein, so that all possibility that the overlay sheet will slip out of position on the cylinder is obviated.

Also to produce a sheet which is perfectly flexible as well as resilient, so that the sheet will not be detri nentally affected by the aet tion of the cylinder in pressing it against the bed, permitting the number of reproductions which maybe printed to be practically unlimited Also to provideacomposition of substances I to be employed in the production of an embossed overlay sheet whichwill enable a sheet having the advantageous characteristics above referred to, to be'produced without the employment of the highly skilled labor usu ally necessary inmake-ready, and which will enable uniformity of results tobe secured.

I accomplishthese objects by providing a powder for embossing the overlay sheet which is composed of a mixture of substances consisting principally, or Wholly, of certain will adhere to the more heavily inked porforms of gum which have been reduced, by a screening operation, to two or more sizes, the larger of; which, when applied to the proof,

tions, or solid tones of the'proof,.witl 1out ad hering to the less heavily inked portions to a substantial extent, and the smaller of which will adhere to all portions which have been inked and has not been absorbed by the paper I or the coating thereon;

which is composed of gums having different fusing points, the gumfrom which the larger sized grains are formed being of a resilient Also by providing an embossing powder nature and having the highest fusing point,

t and the material from which the smaller grains are formed havinga relatively low using point, so that the smaller grains may become fused first, when the sheet is heated,

and will penetrate the paper and then, on further heating, its larger grains will become slightly fused on their surfaces and united to the mass already fused, so that all the material, including thelarge'r grains, will be lines of the shaded portion of the sheet'to which the material was applied and will also act to draw in the unfused, or partly'fused grains from said lines, so that'the margins of the embossed portions will be slightly beveled. The more specific details as to the manner in which the above described, as well as other advantageous results, are secured, are 'more fully described in the following specification,

igs. 1 and2 are greatly enlarged sectional views of an overlay sheet illustrating different steps in my herein'described process.

Fig. 3 isa sectional view on an enlarged scale, showing the application to a press cylind in connection with printing presses of different types, for the purpose of convenience I in description, the type of press which will be referred to hereinafter comprises a reciprocating bed, on which the printing characters are mounted, and a cylinder, having a tympan thereon, composed of several paper sheets.

In producing an embossed overlay sheet embodying my invention, Ipreferably employ a sheet of good quality chalk coated paper, which in many instances, is preferably coated with pummy talc, so that it will absorb any small amount of ink which may be appliedby the high light portions of the printing characters, and prevent subsequent adhesion of the embossing, powder to such; portions, thereby avoiding the necessity of removing the embossing material from such portions, as these portions should not be er. While the overlay sheet may be employed in connection-with the accompanying draw-, 1n s,1n which:

inked at all in printing and the pressure. of

the cylinder thereon should not be in any -way increased by the presence of the overlay. A proof of the: printing characters is ,then taken off on the sheet withthe ordinary ink with which the press is supplied;

and all-impression is also taken on the tympanv for positioning purposes. The proof sheet will be most heavily inked on the solid tone portions of the-proof and more light- 1y inked on the middle and grey'tone portions thereof, the remainder of'the process,

' briefly outlined, being as follows p The embossing powder, hereinafter more specifically described, is then dusted or run over the freshly printed surface, so that it comes in contactwith all parts thereof, and

then the surpluspowder is shaken off, .by

suspending it from one edge and tapping it sharply, 'so that the only grains of the powder which remain are those which have comedirectly in contact with the wet ink. Thesheet is then held horizontally with its coat.- ed side up, and heated on its'under side, preferably by holding it over an electr1c heater, until all the grains which have adhered to the sheet take on a glazed appearance, and then the sheet is ready to be placed on the press cylinder beneath the tympan, in register with theimpressions which has been made thereon.

As the result of much 'experlmentation, I

have ascertained, that, in employing an embossing powder for this purpose, particularly when largely composed of substances of the gumming nature which I employ,- grains of a certain size will adhere to the more heavily inkedsurfaces, but will notibe retained to any substantial extent by the more lightly inked portions, {when the surplus powder is shaken off as above described,

and that grains of a smallersizefwill adhere under these conditions"'t6,both the heavily and lightly inked surfaces; Thatis, I have ascertained that indefinite relation, within certainlimits, existsbetween the size of'the grains and the extent toiwhich a surface -must be inked to retain the grains; I have further" ascertainedg thatx grains of a size which will adhere itothe middle and grey tone surfaces will not sufiicientlv' emboss the solid tone portions,'as practically. no grains compound, although, under some conditions -to-the solid tone .and the smaller grains will fill .in the spaces.

the employment of grains of an intermediate size is de'slrable and under other conditions I have found it desirable to employ grains of as many as six different sizes. For ordinary purposes I provide a compound which preferably comprises a suitable proportion of a gum knownfcommercially-as copal gum, which fuses at approximately 200 0., and

which has been passed through an mesh screen, and a suitable proportion of acon1- mercial gum, known as dammar fuses. at about 120? V I gum, which n C. and which 'hasbeen passed through' a 150 mesh'screen. 'While I consider these sizes particularly desirable,

advantageous results ma'y be: secured with grains of these materials'which approximate thereto, as the grains of each size may be larger or smaller without.

made slightl materially afflicting the results, although the approximate relative proportion of the sizes should be maintained. When to the freshly printed grains of copal gum will ordinarily adhere portion only of the picture,

therebetween; as indicated on agreatly enlarged scale in Fig. 1 in which a sheet a is indicated as having b applied sheets the larger 0th the larger sized 1 l grains 1; and smaller sized grains 0 adhering to the heavily inked surface portion d ofthesheet and the smaller sized grains 0 adherto the less heavily inked surface e.

ing

further include-in the compound a suitable quantity of either Bergundy pitch, or

.carnaubawax, the-l-a'stjnamed being prefermoi;-

able, as it isthe least expensive. qThis substance is reduced to approximately the same degree of fineness as the dammar gum, and

is thoroughly mixed therewith. The meltmg: ints ofthe'carnauba-waxis approximate y- (1., so that, when the sheet is heated, boththe dammar gum and the carnauba wax become completely fused before the copal gum is fused to any substantial extent, particularly also because they have been re duced to a greater degree of fineness.

As a result of the heating operation, the

carnauba wax-will fuse first and will penetrate the paper and the dammar gumwillfuse immediately thereafter, or at practically the-same time, so that the grains of cop-a1 gum will be surrounded and more or less coated by this fused material. On still further heating, the surfacesof the grains of copal gum will be slightly fused and will thus unite with the material already fused and thus will be securely attached to the paper on cooling.

To secure this result, the heating operation is continued until the powder on the sheet.

assumes a gloss appearance, which is due tothe presence 0 the dammar gum, and pro-'- -vides an accurate guide to the operator, so

that, with reasonable care, over heating, or

heating to an extent suflicient to destroy the resiliency of the copal gum will be prevented,

' while sufficient heat will be supplied to fix the materials to the sheet, as indicated in Fig. 2. However, if these ingredients alone were employed in the manner above described, the fused material would flow over thelines between the portions having different degrees of shading or tone, with the resultthat these lines would be distorted, so that the results wouldbe unsatisfactory. v

I have'discovered that this difficulty may be entirely avoided-by also combining with theother substances above specified, a suitable quantity of a substance which Will act as an astringent, and has a low melting point, forexample :gu m sumac, tannic acid,-or alum. Of these substances the gum sumac is considered preferable. .This substance is also reduced to approximately the same degree of fineness as the dammar gum and is thoroughly mixed with all the substances above specified. It also has a fusing point which approximates to that of dammar gum and the 'carnauba wax and, as it is reduced to the same-fineness as these substances, will begin to fu's'eat practically the same time that the other smaller size grains begin to fuse. As soon as the astringent, or gum sumac begins to fuse, 1t also begins to contract and thus contracts the liquid formed by the fusion of the other substances with which itis mixed, and acts to draw together the unfused or slightly fused grains of copal gum, so that the spreading out of thefused mass or thegrains beyond the space on which they are deposited, is prevented. The material which is deposited onfany portion of the sheet, which is fused, is contracted and the .unfused or partly fused grains are drawn together, so that the material, as a whole, is slightly drawn 40 away from the edge of the space on-which it was deposited, and, as a result, the embossment on the finished overlay sheet is slightly beveled or rounded'at the li ne between the solid tone of the picture and the adjacent tones of lighter shade, as indicated in Fig. 2.. Tnis result is important, not only for the reason that the embossing substance is prevented from spreading onto adjacent shadows of less depth, but also because, when in use, the increased pressure on any portion due to the embossment might cause an increase of -pressure on adjacent portions, if the embossment retained its full thickness to theedge, and, as a result, the line between the corresponding adjacent portions of the printed picture would be distorted, but if the edges of the embossments are slightly beveled, as above described,'the possibility of such an occurrence is 'avoided. The ingredients of the compound in the approximate portions whichI preferably employ in securing the' abovedescribed results "are as follows:

45% copal gum, screened to mesh, and

65.fusing at about 200 C.

35% dammar gum, screened to 150 mash, and fusing at'about 120 C.

8% gum sumac, screened to 150 mesh,'and fusingat about 120 C.

' 12% carnauba wax, screened to 150 mesh, and fusing at about C. v

It 'will be understood that various other forms of gums, resins and astringents, may be substituted for those above specified,--as' anyof these substances having similer char-' acteristics are considered tobe eqgxvalents. 7

The 'primary functions of'the di ere t ingredients above specified are as f ow s: The copal gum provides a-,h embossment for the solid tones and a resilient pebbly surface. a Q

The carnauba wax,by melting first, penetrates the paper and serves as an anchor for. the embossment. v The dammar gum, by melting immediately thereafter, acts as a binder, attaching itself t the penetrating wax and to the fused surface of'the copal gum rains and also serves as an embossment for t e middle tones.

The gumsumac acts asan astringent to prevent the fused material from flowing over the lines between different shade tones and todraw in the grains so that the'edg es of 'on the cylinder f beneath the tympan g, as

shown in Fig. 3, this roughened surface will become, by reason of the pressure on the tympan, slightly indented in the latter, 01f willhave a strong frictional engagement therewith, so that all possibility of slipping of the overlay sheet on the cylinderwill be prevented. Under the action of the cylinder in pressing the paper to be printed against the printing characters, as h, the embossment on the overlay sheet will 'be pressed flat by the cylinder at the point offcontact. of the latter with the bed, but, as soon as the pressure on any portion of the embossment is removed, it will be restored to normal by its resiliency, as indicated in Fig. 3. The heavy compression to which the overlay sheet is subjected by thecylinder has no detrimental 2 effect thereon, as the embossment on the sheet is both resilient and flexible, so that the sheet maybe used practically indefinit'ely, or as long as it would be likely to need to be used for any run of the-press.

,The extent of the embossment on the different tones of the proof sheet may be somewhat varied by yarying the sizes of the grains in the embossing powder, but'where extra I heavy pressure on the printingch'a'racters or printing from-half-tone cuts, orplates, and

enabling results tobe secured which, so far as I am aware, cannot be secured by. any of the other methods herein referred to, is also advantageous in printing from type where heavy and-light characters are to be printed. I claim: a

1. The methodof makin an embossed overlay sheet for makerea y in printing which consistsin-covering the freshl inke surface of a proof sheet with an em ossing powder composed of a mixture of grains of a suitable material composed of a predetermined proportion of grains'of a size which will be retained to a substantial extent b the more heavily inked portions only of the s eet and a predetermined proportion of grains of smaller-size which will be retained by both 3 0 the heavily andlightly inked portions, shaking off the surpluspowder. and then fixing the powder whichohas-been retained to the sheet. v

2. The method of making an embossed overlay .sheet for makeready in printing, which consists in covering the freshl inked surface of a proofsheetwithan em ossing] powder composed of a'mixture of grains ofgum composed of a predetermined proportion of grains of a size which will be retained to a substantial extent by the more heavily inked portions only of the sheet, and a prede termined proportion of grains of gum of a relatively small size which will be retained by both the heavilyand lightly inked portions thereof, then shaking oif the surplus powder" and then heating the sheet to fix the remaining powder thereto. 4

3. The method of makin an embossed overlay sheet for makeready in 'rinting which consists in covering the fresh y inked surface of a proof with a powdered gum composed of a mixture of grams, a predetermined-proportion of which are graded to a and by their fusionto fix the larger grains to the sheet.

4:. The method of makin an embossed .65 overlay-sheet for makerea yin printingsize which will-be retained by the more heavl which consists in covering the freshly inked surfaces of a proof witly-a, powdered resilient gum composed of grains of a size suflicient to be retained by the more heavily inked porheating the sheet to fuse the smaller grains and by their fusion to fix the larger'grains to.

the sheet.

5. The method of making an embossed overlay sheet for makeready in printing which;

consists in covering the freshl inked surface of a proof sheet with an em ossing powder comprising a resilient um composed of grains of a size which will e, principally retained b the more heavily inked portions only of t e sheet and mixed with a comosed of grains of relatively small slze, shaking off the surplus powder, heating the sheet to fuse the smaller grains and cause the fused material to become attached to-the sheet and become fused to the larger grains to fix the latter on the sheet.

6. The method of makin an embossed overlay sheet for makerea y in printing which consists incovering the freshl v inked surface of a proof sheet with an em ossing powder comprislng a resilient gumcomposed of grains of a size which will be retainedprincipally by the more heavily inked portions only of the sheet and a substance composed of relatively small grains and'having a substantially lower melting point than that of the larger grains,-shaking ofi the surplus powder, heating the sheet to fuse the smaller. grains and cause the fused-material to become attachedto the sheet and tocause surface fusion of the larger grains to fuse the latter to the fused material and to the sheet.

powder comprising a mixtureof a resilient gum composed of grains of relatively large size and high fusing point which will adhere principally to the more heavily inked por-' tions only of the sheet and a gum composed of grains of. relatively small size and low melting. point and heating the-sheet to fuse the smaller grains and fix the larger grains. to the sheetwithout substantial fusion there- 8. The overlay, sheet. for makeready in printing which consists in covering the freshl inked surface of va proof sheet with an em ossing powder comprising a mixture of a resilient gum composed of grains of relatively large size and high fusing point which will adhere principally to the more heavily-,inked portions only of the sheet and two similar materials composed of grains of relatively small method of making an embossed size, oneof which has a relatively low fusing point and the other a fusing point intermediate that of the other materials, shaking off the surplus material, heating the sheet to fuse the grains of lower fusing points successively to permit the material first fused to penetrateth'e sheet and to surround the larger.

grains with the fusion of both materials and fix the larger grains to the sheet.

9. The method of makin an embossed overlay sheet for makerea y in printin which consists in covering the freshly inke surface of a proof sheet with a powder comprising a fusible granular embossing material mixed with a fusible granular astringent material and then heating the sheet to fix the powder thereto.

10. The method of making. an embossed overlay sheet for makerea'dy in printin which consists in covering the freshl inke surface of a proof with a fusible em ossing powder comprising a powdered gum mixed with a powdered astringent and heating the powder retained by the ink to fix it to the sheet. v

11-. The method of makin fan embossed overlay sheet for makerea y in printin which consists in covering the freshly inke surface of a proof with an embossing powder comprisin a powdered gum having a rela-' Q powder comprising a powdered gum divided lower melting point than that of the gum size, and then heating the sheet to into grains of a relatively large size'mixed with an astringent having a substantially small se the astringent and then fuse the gum to the sheet. 13. The method of making an embossed overlay sheet for makeready in. printin and divided into grains of relativel which consists in covering the freshl inke surface of a proof sheet with anem ossing powder comprising a powdered gum divided into grains of a relatively lar e size mixed with a um'and an, astringent, oth'of which .have su stantially lower, melting points than that of the gum from which the larger grains grains to the shee are formed, and are divided into relatively small grains, and then heating the sheet to fuse the smaller grains and fuse the larger 14:. The 'method of making an embossed overlay sheet for makeready in printing which consists incovering'the freshly inked surface of a proof sheet with an embossing powder containinga powdered gum and a powdered astringent, shaking off the surplus powder and then heatingthe sheet to which comprises two powder fuse the gumsufliciently to fix it to the sheet and by the action of the astringent when heated to draw the gum away from the margin of the inked spaces to which has adhered.

15. An embossing overlay sheets for ma eread in printing gums, one being composed of large grains and the other of relatively small grains. 16. An embossing powder for making overlay -sheets for makeread in printing which comprises two powdere gums, one being composed of large grains having a high melting oint and the other of relatively small grams having a relatively low melting point.

ppwder for making.

17. An embossing powder for use in making an embossed overlay sheet, which consists of powdered gum which has a tendency to flow on the sheet when fused, mixed with a powdered astringent which has the property of counteracting said tendency of the gum.

18. An embossing owder for use in making an embossed over ay sheet which consists of powdered ains. of gum mixed with a 'owdered bin er and a owderd astringent 0th of which having a fiising pointsubstantially lowerthan that of the gum.

19. An embossing powder for use in the production of an overlay sheet of the character described which is composed of powdered copal gum divided into rains of relatively large size, and powdered vided into grains of relatively small size.

20. An overlay sheet for makeready having a rough surfaced resilient embossment, adapted to become indented in the tympan of a printing press, to hold the sheet from displacement and permit temporary depression of the embossment,

ing an embossment of resilient grains of gum dammar gum di- 21. An overlay sheet for makeready havforming a roughened surface, adapted to bei come indented in the tym an of a printing press, to hold the sheet rom displacement and permit temporary depression of the embossment. 22. Anoverlay sheet for makeready havingportions thereofembo'ssed with grains of.

resilient gum embedded ina fused mass of gum which is fused to the sheet.

23. An overlay sheet for use in makeready for "printing a picture in which the solid tones of the picture on the sheet are embossed with" necte sheet.

24. An embossing powder for making by surface fusion to the surface of the overlay sheets for makeready in printing which comprises a plurality of sizes of rainsof fusible gum mixed in predetermine proains of a resilient gum which are conportions, the grains of larger size being adapted to be retained by the more heavily inked portions only of a freshly inked roof sheet, and the size-of the smaller grains eing graded to correspond approximately to the weight of the ink on tho more lightly inked portions of the shoot, to secure an embosslnent thereon approximatel Corresponding to the weight of ink on the' ifi'eront portions thcroof.

In testimony whereof, I have signed my name to this specification.

ARTHUR L; SMITH;

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