US1370418A - Process osi correcting printing-plates - Google Patents

Description

S. E. DITTMAN.

PROCESS 0F CORRECTING PRINTING PLATES. APPLICAT'xoN mib AuG.2o. 1919.

1,370,418.l f Patented Mar.1,1921.

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vPROCESSv 0F COR-HEQTING PRINTING PLATES..` .APPLlATloN FILED AuG.2o. 1919.

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S. E. DfITTMAN.

PROCESS 0F CORRECTING PRINTING PLATES.

Y APPLICATION FILED we zo, 1919.

' l 370,41 Patented Mar. 1, 1921'.

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UNITED STATES PATENT oFFics.

SAMUEL EDWARD DITTMAN, or rmooinivu,Y NEW YORK.

PROCESS OF CORRECTING PRINTING-PLATES.

Application filed August 20, 1919.

7 'o al] 1i/10m t may concern Be it known that I, SAMUEL E. Drr'rMAN, a citizen of the United States, residing at Brooklyn in the county of Kings and State of New York, have invented a certain new and useful Improvement in the Process of llorrecting Printing-Plates, of which the commercially impossible to produce a level plate of uniform height by theusual methods because of the great care7 time and skill required by the methods now in vogue, and the tact that the `usual shaving opereation to which the plate is subjected after it is treated to level the printing face thereofD causes inaccuracies in the height ofthe plate.

rlhe usual method or practice of utilizing these imperfect plates consists in providing the imjn'ession platen or cylinder of the printing press with a make-ready sheet upon which overlays or projections are built corresponding 'with the low portions ofv the` plates andwhich serve to torce the sheet to be printed into the low portions of the plates to secure a full impression. However. this forcing of the sheet out of its true or ideal printing relation tends in many cases to impair the work. Also in long runs the make ready sheet becomes subject to a shifting action with respect to the impression plfu'cnv and the printing plates owing to its pliahility or expansive qualities under vary; g atmospheric conditions, which .not only impairs the printing but causes unequal wear on the plates.

It has also been the practice to place an underlay sheet at the back of the plate upc-n which projections are built corresponding with the low portions of the plates to increase the thickness thereof at certain points, but this is unsatisfactory in that the plate does `not have a solid back or seat much lessiui loven one whereby the plate` rpcks Specification of Letters Patent.

Patented Mar. 1, 1921. Serial No. 318,720.

and gives and interferes with the printing'. Underlays are subject to the same shifting action as 'the overlays, and are equally unsatisfactory particularly where used to correct the inherent inequalities in the plate.

lVhere these imperfect plates are utilized by overlays and underlays the making ready of the plates is a long tedious operation requiring great skill and application. However, where the plates are of uniform thickness throughout and have a solid back or seat it is a relatively simple operation to make ready in that it is only necessary to overlay sutlicient-ly to exert more pressure on the heavily inked portions of the plates, such an overlay not being subject to the inherent disadvantages thereof to such an extent as to be unduly troublesome.

' Other methods which have been proposed for making ready these imperfect plates require great skill and application in the practice of the same and are subject to' practical difliculties which are very hard to overcome.

The object of my invention resides in the provision of a method for accurately and preferably permanently correcting a plate so that it has an even printing face, a uniform thickness throughout and a solid back or. seat, and which does not require great skill and application in the practice thereof.

The method is adapted to be practised independently of and prior to the use of the plates'upon a printing press.

In describing theinvention in detail, reference is had to the accompanying drawings, forming a part of this specification, Y and wherein like characters of reference are used to designate corresponding parts throughout the several views, and in which:

Figure l is a partially sectional side elevation of a machine for testing the thickness of the printing plates to be corrected ;A Fig. 2, a sectional view of the same taken at right angles to Fig. 1 Fig. a. partially sectional elevation of a machine for seating the plates; Fig. 4t, a sectional view of the latter machine taken at right angles to Fig. 3; Fig. 5 is an enlarged bottom plan view of the correction sheet hereinafter referred to; Fig. 6 an enlarged exaggerated sectional elevation of a printing plate which has been'corrected by the method of my invention; Figs; 7 and 8 are partial enlarged sections of' the testing machine in elevation similar to F ig. 1 showing the use of this l l O machine under certain circumstances hereinafter described; and Fig. 9 is a partial enlarged section of the seating machine in elevation similar to Fig. 3 showing the use of this machine under certa-in circumstances hereinafter described.

In the drawings, numeral l designates the frame of the testing machine, including the base 2, which constitutes a lower pressure member, arranged. to coact with the upper pressure member 3, slidably mounted in the frame, and actuated for vertical movement by the screw 4, threaded in the yoke of the frame, and provided with an operating hand-wheel 5. At its lower end the screw is formed with an ordinary swivel 6, arranged to turn within a cap 7 fixed to the upper pressure member. The machine is constructed of metal throughout, the adjacent inner faces of the pressure members constituting true unyielding surfaces, correspondingly shaped to suit the required form of the corrected printing-plates, indicated by the numeral 8. Fixed to the pressure face of the upper pressure member 3 are a pair of bearer-bars 9, adapted to engage the opposite face of the lower pressure member 2, and to space the members apart under pressure a distance corresponding with the required thickness of the plate. Clips 10, of any approved form, are provided for the lower member 2 for detachably holding the plate during test in a true position.

The initial step in the process consists in taking a test of the plate 8 to be corrected to determine the variations in height of the printingplate. This is preferably accomplished by taking a correction or test sheet 1l, preferably consisting of paper similar in kind to that commonly used for preparing the ordinary make ready. The plate 8 being inked in the usual manner, an impression is taken thereof upon the correction-sheet. This impression is preferably taking in the testing machine as illustrated in Figs. l and 2, the plate 8 being adjusted upon the lower pressure member 2 face uppermost and the correction or test sheet ll being laid thereon for receiving the impression, whichl is effected by impressing the same upon the plate by means of the pressure member 3 actuated by the screw 4 and the hand-wheel 5, the bearer-bars serving to avoid excessive compressing` or crushing of the plate. See Fig. i'. These faces being true and unyielding surfaces unyieldingly impress the sheet upon the printing face of the plate and bring out an exact impression and clearly show the defects or variations in the thickness of the plate by the comparative hardness of the impression upon the sheet. See Fig. 5 in which the imprinted portion 12 indicates the portion of the plate which is thinner than the heavily inked portion 1?- of the` correction-sheet. The aim in the present case is to present the defects as exaggerated as possible in order that they be the more readily observed and. corrected. It will be clearly seen that this method of taking a test impression upon a sheet for correction purposes is directly opposed tc that carried out in the ordinary proof-press or printing-press wherein soft packing is used on the faces of the pressure members to cover up and hide the inequalities of the plates.

In order to determine with great accuracy the nature of the low portions of the plate a number of test impressions are taken and sheets of different yielding qualities are interposed between the true unyielding surface of the upper pressure member 3, adjacent the face of tbe plate, during the several impressions. .See Fig'. 7, in which only the correction or test sheet ill. is interposed, and see Fig. S in which a test sheet and a second sheet 29 is interposed between the surface of impression member 3 and the face of the plate, the test sheet being next to the face of the plate. Due to the fact that as the yielding quality of the pre1-isure with which the test sheets are impressed upon the plate increases, the defects of tl e plate show less upon the correction-sheet and the true character and depth of the low portions may be determined in this manner. T hus only the thinner portions of the low portions of the plate will show upon the test sheet 28 in Fig. S, and the thicker portions of the lower portions will show on the test sheet 1l in Fig. 7 in addition to the thinner portions. See Fig. 5 in which only the thinnest portion SO, inclosed within thc dotted line, would be unprinted if the inpression were made under the circumstances shown in Fig. 8.

By the use of this method of testing the plate a very exact definition of the ina:- curacies in the height of the plate may be obtained, thereby permitting a correction in the first inst: nce which corresponcs f closely with the inaccuracies in the height the plate, thus obviating the necessity of re-v correcting the pla-te in pravtifally all cases.

Then the indicated low portions of the plate are built up by ap )lying a suitable substance lt, see Fig. G, to the back surfacc of the plate at the indicated low portions thereof to a thickness substantially corresponding with the relative difference in the thiy kness of the plate.

This is preferably accomplished by building up with a suitable sub-tance the indicated low portions on the correction-sheet at the portions thereof corresponding with the low portions of the plate on its upper or unprinted side to a thickness substantially corresponding with the relative difference in the thickness of the plate. In order that the low portions of the plate may be indicated lili? lil . substance in the plate.

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upon the imprinted side of the correction sheet the unprinted side of the correctionsheet is pressed against a carbon sheet and the low portions outlined with a stylus on the printed side of the correction-sheet. The building up of the correction-sheet may be accomplished by the use of a variety of substances but preferably by the use of a substance having a plate engaging surface adapted to adhere to the plate during the embedding operation, hereinafter described, to effect the permanent embedding of the A substance of this character which l have found to work very well where the hea-t is used during the em* bedding operation, as hereinafter described, is a mixture of black marine engine enamel and Portland cement, the proportion of cement being less than that of the enamel. Where necessary two or more coats of this mixture are applied each coat being dried (not baked) by the application of a low degree of heat before another coat is applied. TWhere necessary cement is sprinkled upon the wet mixture to obtainy greater thickness and after this is dried a thin coat of enamel is applied to the sprinkled portions and dried to obtain perfect adhesion to the plate. The built-up correction-sheet is'then transferred to the back of the plate and adjusted correspondingly opposite thereon (the high pointsbf the sheet op osite the respective low points of the platei Then the substance as so applied is embedded in the baclt surface of the plate to form a plate having an even printing face, a uniform thickness throughout and a solid back or seat. lllhere, as is the case with the preferred substance hereinabove described, the substance has its plate engaging surface adapted to adhere to the plate it is permanently embedded inwthe back of the plate during the embedding operation with ob* vious advantages.

This embedding of the substance in the back of the plate is accomplished by sublieeting the plate and substance, applied as above described, to pressure between parallel, true and unyielding surfaces with the face and haelt of the plate in controlled re lation with respective surfaces whereby, if

there bc any inaccuracies between the thick-V ness of the substance and amount Vthat the plate should be built up the unyielding true pressure exerted will accommodate the same to accurately even the plate cmsing displacement in the effected portion of the plate or the building-up material or both depending upon the relative plasticity of the same. This embedding of thesubstance in the back of the plate is preferably accomplished by the use of the seating machine illustrated in Figs. fl, and 9. `Where this is used in the practice of the invention the plate is positioned in the seating machine with the building up substance applied to the back thereof as above set forth, see Figs. 3 and 4t where the numeral 8LLV designates the plate to be seated; i12, the built-up corre tion-sheet; l5, the frame; 16, the combined base and lower pressure member; 17, the upper pref*- sure member, vertically movable in the frameand provided with a pressure screw and hand-wheel, similarly arranged. as those described for 'the testing machine. In a like manner to the testing machine, the pressure members of the seating-machine have parlallel, true and unyielding faces adapted to be spaced apart under pressure by the bearer-bars 18, fixed to the upper member 1'?.

.In the embedding operation the plate is preferably heated to a somewhat plastic condition, about 4500 F., when subjecting it to pressure to facilitate the embedding of the building-up substance into the back of the plate, and where the above described building-up substance is used to facilitate the ad: hesionbf the same to the baclr of the plate. To effect this the pressure members of the seating machine are provided with heating chambers 19 and 20, in which are disposed gas burners 2l which are connected with gas pipes 22 and 23, leading from a convenient source of gas supply, the pipe 22 being fieri-- Yble for the accommodation of the vertical movement of the pressure member 17 to which it is connected. The end walls of the chambers 19 and 2O are provided with apertures 2e through which the products of combustion may pass. In practice, see Fig, 9, an oiledpsheet of hard paper 25 is interposed between the built-up correction-sheet and two news sheets 26 or other thin paper are placed between the oiled sheet and the lower pressure member l@ to provide a slightly yielding cushion to accommodate practical inaccuracies in theI apparatus and method, and where the face of the plate is delicate and liable to be damaged by the required pressure two news sheets 27 or other thin paper are interposed between the upper pressure member 17 and the face of the plate to protect the face of thev plate. The oiled sheet.r prevents the correction-sheet from sticking to it or the sheets 26 or the adj acont pressure member if these sheets are not used.

By reason of the fact that the plate and building-up substance are subject to p essure between parallel true andl uuyielf surfaceswith the face and bacia `of the pl in 'controlled relation withl respect to surfaces. the pressure exerted is intensi on the building-up substance, thus brinni 2' the face of the plate to vthe proper level. f

necessary, and embedding` the -buildingup substance in the back of the plate. lf after this is effected the thickness-of the plate at l l) l) the point where the building-up substance is embedded is thicker than remainder of the plate, the pressure is still intensified on the built-up portion and operates thereon to displace the effected portion of the body of the plate or the building-up substame or bot-h, dein-inding` upon the relative plasticity of the saine? so that the thickness of the built-up portion of the plate is reduced until the pressure is exerted throughout the plate at which. time the builtin) portion oi the plate is the saine thickness as ther re mainder of the ilate. Thus an automatic check is provided against overincreasing the thickness of the plate at the built-up portions thereof. The portion of the plate which is not built-up is effected in a similar manner 'where certain portions thereof are thinner' than others. the pressure being intensified en the thic r portions thereof and displacing the same until the thicker portions are the same level as the thinner portions thereof. ieca of this action l lind that in the practice o the method in its pre-H ferred embodiment it is unnecessary to apply any building-up ::uli;iitance to such por` tions of the plate as are only slightly thin ner.

I final that a pressure between 200 and 250 pounds per square inch of the plate is suliicient to effect the desired result .vhere the above specified heat is used.

After the building-alp substance 14 has been embedded in the back of the plate, as designated in Fig. 6, the correction-sheet may be removed by scraping it off preferably after first soaking the same with Water. `\fter the removal of the correction-sheet the back of the plate may be painted with an aluminum paint to prevent the building-up substa heated in other operations such as in bending a straight plate for a rotary printing press, as it is obvious that the present invention may be practised upon a straight plate as Well as a curved plate.

By the practice of the present invention in its preferred manner it will be noted that a permanently corrected plate of uniform thickness is produced having an even printing face and a solid back or seat, and that the method does not require great skill and application to produce an accurately corrected plate and the method has an inherent corrective action which overcomes to a great extent inaccuracies in the plate not attempted to be corrected by the operative and inaccuracies arising because of the opcratim in the practice of the method,

While I have shown and described the method of my invention as applied to a plate, the proper printing surface of which should be disposed in one level, I contemplate the use of the invention as applying to a plate, the character of the printing surface of which requires that certain areas of the surface of the plate'be elevated from sticking when the plate isfrom the level of other areas thereof, to effect the leveling of the surface in each of such areas and the provision of a solid back or seat therefor` whereby the printing from each of such areas will be uniform and Will require less printing pressure to effect a uniform print from each of such areas than otherwise, this accurate leveling being practically impossible to obtain with sullieient accuracyT by any of the methods, which have been heretofore proposed and practised, because they depend entirely upon the skill and application of the operative Whereas the method of my invention of itself provides an automatic check on the amount that the lo portions of a given area are raised to prevent such low portions being` thicle cned too much at the loiv portions thereof as hereinbefore set forth. Furthermore I con template the use of the invention before or after or at the time the areas of the surface of the plate are raised, for reasons ab ve setl forth, but preferably after such raising of such areas is effected so that inaccuracies in the raising process may be corrected as `well as other inaccuracies in the level of such areas.

In carrying out the improved process, or dinarily. only a single operation, though the process may be repeated Where necessary, is required.

Vhat I claim as my invention and desire to secure by Letters Patent7 is;

l. The process of correcting a printing plate con'isti in taking a test of the plate to determine the variation in height of the printing plate, building up the indicated low portions of the plate by applying a suitable substance to the back surface of the plate at the indicated low portions thereof to a thickness substantially corresponding ivith the relative difference in the thickness of the plate and embedding the substance in said back surface of the plate as so applied by subjecting the plate and substance to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

The process of correcting a printing plate consisting in taking a test of the plate to determine the variation in height of the printing plate, building up the indicated lov: portions of the plate by applying a suitable substance to the back surface of the plate at the indicated low portions thereof to a thickness substantially corresponding with the relative difference in the thickness of the plate and embedding the substance in said back surface of the plate as so applied by heating the plate to a plastic condition and subjecting the plate and substance While the plate is in said plastic condition to pressure between parallel unyelding true surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

The process of correcting a printing plate consisting' in taking a test impression of the plate between unyielding true surfaces to determine the variation in height of the printing plate, building up the indicated low portions of `the plate, by applying a suitable substance to the back surface of the plate at the indicated low portions thereof to a thickness substantially .corresponding with the relative difference in the thickness of the plate and embedding the substance in said back surface of the plate as applied by subjecting the plate and applied substance to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

i. The process of correcting a printing plate consisting in taking a test impression of the plate between unyielding true surfaces to determine the variation in height of the printing plate, building up the indicated low portions of the plate by applying a suitable substance to the back surface of the plate at the indicated low portions thereof to a thickness substantially corresponding with the relative difference in the thickness of the plate and embeddingr the substance in said back surface of the plate as so applied by`heating the plate to a plastic condition and subjecting the plate and substance while the plate is in said plastic condition to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

5,. The process of correcting a printing plate consisting in taking a test of the plate upon a correctionsheet to determine the variation in height Vof the printing plate, building up the indicated low portions on the correction-sheet at the portions thereof corresponding with the low portions of the plate to a thickness substantially corresponding with the relative difference in the thickness of the plate, transferring the builtup correction-sheet to the opposite side or back of the plate and embedding said huiltup portion of the correction-sheet therein by applying pressure to the plate and built-up correction-sheet as so transferred to pressure between parallel unyielding surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

6. The process of correcting a printing plate consisting in taking a test of the plate upon a correction-sheet to determine the variation in height of the printing-plate, building up the indicated low portions on the correction-sheet at the portions thereof corresponding with the low portions of the plate to a thickness substantially `corresponding with the relative difference in the thickness of the plate, transferring the builtsheet as so transferred while the plate is in p said plastic condition to pressure between parallel unyielding true surfaces'with the face and back of the plate in controlled relation with respect to these surfaces.

7. The process of correcting printing plates consisting in taking a test of the plate upon a correction-sheet by means of pressure between unyielding true surfaces to determine the variation Vin height ofthe printing plate, building up the indicated low portions on the correction-sheet at the portions thereof corresponding with the low portions of the plate to a thickness substantially corresponding with the relative difference on the thickness of the plate, transferring the built-up correction-sheet to the opposite side or backof the `plate and embedding :said

built-up portion of the correction-sheet therein by subgectingthe plate and built-up,

correction-sheet as so transferred to pressure between parallel unyielding surfaces lwith the face and hack of the plate in controlled relation with respect to these surfaces.

8. The process of correcting printing plates consisting in taking a test of the plate upon a correction-sheet by means of pressure between unyiclding true surfaces to dctermine the variation in height of the printing plate, building up the indicated lowv portions on the correction-sheet atV the portions thereof corresponding with the low portions of the plate to a thickness corresponding with thel relative difference in the thickness of the plate, transferring the built-up correction-sheet to the opposite side or back of the plate and embedding said built-up p0rtion of the correction-sheet therein by heating the plate to a plastic condition and subjecting the plate and built -up correctionsheet as so transferred while the plate is in said plastic condition to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

9. The process of correcting printing plates consisting in taking a test of the plate upon a correction-sheet to deterininethe variation in height of the printing plate2 building up the indicated low portions of the correction-sheet at the portions thereof corresponding with the low portions of the plate to a thickness substantially corresponding with the relative difference in thickness of the plate, transferring theY huilt-up correction-sheet to the opposite side or back of the plate, heating the plate to a plastic condition and embedding the builtup portion on the correction-sheet therein while the plate is in plastic condition by subj ecting the plate and the built-up correction- Sheet as so transferred to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled relation with respect to these surfaces.

10. The process of correcting printing plates consisting in taking a test of the plate upon a correction-sheet by means of pressure between unyielding true surfaces to de` termine the variation in height of the printing plate, building up the indicated low portions on the correction-sheet at the portions thereof corresponding with the low portions of the plate to a thickness substantially corresponding with the relative difference in the thickness of the plate, transferring the built-up correction-sheet to the opposite side or back of the plate7 heating the plate to a plastic condition and embedding the builtup portion on the correction-sheet therein While the plate is in said plastic condition by subjecting the plate and built-up correction-sheet as so transferred to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled "n relation with respectto these surfaces.

11. The process of correcting a printing plate consisting in taking a test of the plate to determine the variation in height of the printing plate, building-up the indicated low portions of the plate by applying a suitable substance having a surface adapted to adhere to the plate to the back surface of the plate at the indicated low portions thereof to a thickness substantially corresponding with the relative difference in the thickness of the plate and permanently embedding the substance in said back surface of the plate as so applied by subjecting the plate and substance to pressure between parallel unyielding true surfaces with the face and to determine the variation in height of the printing plate, building up the indicated low portions of the plate by applying a suitable substance having a surface adapted to adhere to the plate to the back surface of the plate at the indicated low portions thereof to, a thickness substantially corresponding with the relative difference in the thickness of the plate and permanently embedding the substance in said back surface of the plate as so applied by heating the plate to a plastic condition and subjecting the plate and substance while the plate is in said plastic condition to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled relation with respect to said surfaces.

13. The process of correcting a printing plate consisting in taking a plurality of test impressions of the plate between true and unyieldi'ng surfaces and interposing sheets having different yielding qualities between the face of the plate and the adjacent surface during the several impressions, building up the indicated low portions of the plate by applying a suitable substance to the back surface of the plate at the indicated low portions thereofl to a thickness substantially corresponding with the relative difference in the thickness of the plate and ernbedding the substance in said back surface of the plate as so applied by subjecting the plate and substance to pressure between parallel unyielding true surfaces with the face and back of the plate in controlled rela tion With respect to said surfaces.

In witness whereof I hereunto affix my signature this 19th day of August, 1919.

SAMUEL EDXVARD DITTHAN.

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