US2114288A - Printing plate and method of making the same - Google Patents

Description

April 19, 1938. A. B. DAVI$ PRINTING PLATE AND METHOD OF MAKINGTHE SAME Filed Aug. 22, 1935 4 Sheets-Sheet 1 April 19, 1938. mm 2,114,288

PRINTING PLATE AND METHOD OF MAKING THE SAME Filed Aug. 22, 1935 4 Sheets-Sheet 2 NVE NTOQ/ fir/7w)" )3. J90 ws f M 3x W (ATTOQN Egys April 19, 1938.

I A. B. DAVIS PRINTING PLATE AND METHOD OF MAKING THE SAME Filed Aug. 22, 1955 4 Sheets-Sheet 3 I PRINTING PLATE AND METHOD OF MAKING THE SAME Filed Aug. 22, 1935 4 Sheets-Sheet 4 Patented Apr. 19, 1938 2,114,288

UNITED STATES PATENT OFFICE PRINTING PLATE AND IWETHODOF MAKING THE SAME Arthur B. Davis, Springfield, Ohio Application August 22, 1935, Serial No. 31,319 Claims. (CI. 41-25) 'This invention relates generally to printing Fig. is a view' similar to Fig. 8 illustrating plates which constitute reproductions of! the the method of forming a modified form of print.- type surface of a type form, engraving or the ing plate.

like, and has more particular reference to the Fig. 11 is a fragmentary sectional view of the 5 formation of printing plates composed in part modified plate attached to a printing press cyl- -5 of moldable material such as synthetic resin. inder.

The general object of the'invention is to pro- Fig. 12 is an elevational view of the preferred vide a new and improved printing plate comform of make-ready sheet. prising a layer of resinous material having Fig. 13 is a section taken along the line 10 molded type projections and itself adhesively |3-l3 of Fig. 12. 10

secured in the molding operation to the surface The invention is susceptible of various modiof an imperforate metalv sheet by which the fications and therefore I do not, by the present plate as a whole may be fastened properly to a exemplary disclosure, intend to limit the inprinting press support. vention, but aim to cover all modifications and 15 Another object is to provide for the novel alternatives falling within the spirit and scope 15 treatment of the printing plates during the of the invention as expressed in the appended molding operation to incorporate make-ready claims.

therein so that in the use of the plates in print- 'In the drawings, the invention is illustrated ing selected solid areas of the type will be emas applied to the formation of a printing plate phasized and the pressure on selected high light It comprising areas ll of molded resinous maareas relieved. terial adhesively secured to an imperforate metal A further object is to provide a method of mounting sheet l2 and having'projections l3 reproducing the type surfaces of original forms standing out in relief and defining surfaces H or engravings which providesfor the eliminacorresponding to the characters or other contion, in a novel manner. of the parts correfigurations to be printed. The areas ll may be 25 sponding to the so-called "dead metal ordicomposed wholly of resinous material or of a narily provided in the engraving. mixture of a base or filler ingredient combined Other objects and advantages of the lnvenwith a resin binder. While any preferred moldtion willbecome apparent from the following able resinous material may be used, it is pre- 9 detailed description taken in connection with ferred, in order to permit the plate to be bentthe accompanying drawings, in which readily to the proper curvature, to employ a Figure 1 is a perspective view of the improved resin having thermoplastic characteristics such printing plate in the process 'of attachment to a as that sold under the trade name of Vinylite.

printing press cylinder. The relatively flexible plate thus constructed as. Fig. 2 is a fragmentary sectional view of the may be attached to the printing press support printing plate attached to the cylinder. or cylinder l6 through the medium of a backing Fig. 3 is a plan view of a make-ready sheet or saddle which,v for purposes of illustration, is used in the treatment of the plate. shown as comprising two plate sections H and Fig. i is a plan view of a sheet used in conl8 hinged together at l9 and adapted to engage dd nection with the removal of the resin from the at their remote side edges with shoulders in the 4 "dead metal areas of the plate. form of flanges 20 formed on the carrying sheet Fig. 5 is a fragmentary perspective view of 92. The section I8 is adjustably secured against the mold from which the printing plate is made. the surface of the cylinder it by clamps 2i. Fig. 6 is a fragmentary perspective view of an When the narrower section ll is swung downoriginal type form or engraving to be reprowardly against the cylinder with the plate iii-45 duced. positioned as shown in Fig. 1, the flanges 20 Fig. 7 is a fragmentary perspective view of will be spread apart and the plate stretched over the mold with one form of make-ready sheet the saddle the free edge of thesection ii being attached to the underside thereof. later fastened down by means of clamps 22.

Fig. 8 is a fragmentary sectional view illus- The printing surfaces of the plate above de-' 5 trating the arrangement of the parts preparascribed constitutes a molded reproduction of the tory to the molding operation. surfaces of an engraving 23 or other type'form Fig. 9 is a perspective view of the finished well known in the printing art. To obtain an plate illustrating the method of removing the accurate replica so that all of the dots for obresin from the non-type areas. taining the'difierent color shades may be repro- 55 duced accurately, a mold 24 formed from the engraving is used in molding the printing areas.

For a piu'pose to appear later, the mold preferably comprises 'a layer 25 of ductile metal, such as lead, having cavities 26 therein corresponding to the type projections to be formed and attached through the medium of a sheet 21 of steel or other reinforcing material to a sheet 28 of ductile metal having a flat machined surface 29 disposed in a plane parallel to the roots of the type cavities. The mold may be formed in the manner described in my copending application Serial No. 736,222, filed July 20, 1934.

The plate molding operation is carried on in a suitable press preferably operated hydraulically and having platens 30 and 3| heated as by gas flames 32 to the temperature necessary for softening the resin ingredients to the degree required for molding. During molding, the mold is supported on the lower platen 3| and covered with a layer '33 of the resin ingredients sufiicient in amount to more than fill all of the mold cavities when in the plastic state. The carrying sheet 62 may be fastened by a filler plate 34 against which the upper platen 30 acts. With the parts thus assembled, the platens are first maintained in close proximity to each other until the resin has been softened properly. Then the platens are moved together under pressure to compress the plastic ingredients to a thickness determined by bearers 35 after which the resin is allowed to set with the back surface of the sheet l2 thus accurately maintained in parallel relation to the type surfaces. Upon cooling, the finished plate may be stripped from the'mold and thereafter bent readily to the proper curvature by reheating to a temperature sufiicient to soften the resin slightly. The surface of the carrying sheet I2 is treated in a manner such as to cause firm adherence of the plastic resin thereto so that the resin areas will not be displaced during bending of the plate or under the stresses applied thereto during printing. This may be accomplished by covering the surface of the sheet 0 2 with cl0th 36 such as muslin to which the resin will adhere readily andwhich in turn may be cemented to the metal by means of a suitable adhesive such, for example, as water glass cement.

Provision is made for ready removal from the molded plate of those areas of the resinous material corresponding to the non-type or so-called dead metal areas 23 of the engraving thereby avoiding the costly operation of routing out these areas to prepare the plate for use in printing. For this purpose, the invention contemplates the introduction between the resin ingredients 33 and the muslin surface of the sheet I2 of a'parting medium corresponding in shape and position to the non-printing areas and acting during the molding operation to prevent the plastic resin material from coming into contact with the selected areas of the treated surface.

Herein this parting medium takes the form of a sheet 31 (Figs. 4 and 8) of manila paper out out to form openings 38 corresponding in shape to but slightly larger than the type areas. To facilitate formation of this mask, a printed impression of the engraving 23 may be formed on the paper sheet 31 in a proving press and the printed areas then cut out to form the mask. The latter is secured detachably to the cloth covered surface of the carrying sheet l2 or placed in proper posi tion above the resin ingredients 33 preparatory to ,molding. As indicated at 50, the resin adheres to the mask which, after molding, may be stripped off from the carrying sheet. In this operation, the thin section 39 of the resin material immediately surrounding the type areas is first scored with a. knife so that it will break readily as the thicker areas are bent away from the plate as illustrated in Fig. 9. Thus, in the finished plate, only the printing areas proper and the thin border 39 therearound remain on the cloth surface. Where there is a dead metal area 5| (Fig. 6) completely surrounded by type areas, the corresponding portion of the resin may be removed by applying a properly shaped piece 52 of paper (Fig. 4) to the resin layer or muslin sheet before the molding operation.

Where several similar printing plates are required, it is the present practice to provide for increasing the printing pressure on the so-called solid areas of the plate and relieving the pressure on the high light areas through the use during printing of make-ready sheets individual to the separate plates. The present invention contemplates a substantial reduction in the cost of the make-ready treatment of a series of duplicate plates through the association with the mold from which the plates are madeof a single makeready sheet which operates automatically during the molding of each plate to properly prepare the plates for printing and in effect incorporate the make-ready details in the plate itself. For this purpose, advantage is taken of the inherent flexibility possessed by the mold 24 when constructed as above described to enable the heights of the selected printing areas formed thereby to be varied relative to each other during the molding operation by the action of a built-up underlay 40 positioned against the flat back surface 29 of the mold.

As illustrated in Fig. 7, the underlay 40 is in the form of a paper sheet having indentations 4| therein disposed opposite the mold cavities corresponding to solid" printing areas upon which the pressure is to be increased during printing. Paper patches 42 may be secured to the underlay sheet opposite the cavities corresponding to the high light areas on which the printing pressure is to be relieved. During molding of the first plate, those parts of the mold which are in register with the underlay sheet will be supported by the latter while the parts opposite the indentations 4| will be depressed by fiexure of the mold under the pressure to which it is subjected. Accordingly, the printing surfaces of the type formed in the depressed cavities will, in the finished plate, project a greater distance from the sheet l2 than the surrounding printing surfaces, this difference in the heights of the printing surfaces being determined by the depth of the indentations 4|. Thus, in the use of the plate in printing, the pressure on the higher areas will be increased, and the solids corresponding to the size and shape of the depressions 4! will be emphasized properly. Similarly the printing pressure on selected high light" areas may be reduced to the desired degree through the provision of the patches 42 of the proper size and shape. Under the molding pressure, these patches flex the mold and raise the roots of the type cavities in register therewith thereby causing the corresponding printing surfaces of the finished plate to be spaced closer to the sheet l2 than the surrounding. surfaces.

Owing to the flexible and ductile character of the lead of which the mold is constructed, the printing areas of the finished plate which are affected by the action of the make-ready details 2 correspond accurately in size and shape to the indentations 4i and the patches 42. sufiicient precision may be attained in the makeready treatment to substantially avoid the necessity of any further treatment in the use of the plate in printing. The lead of the mold will of course take a set in the initial plate molding operation, but will nevertheless respond to changes in the underlay sheet that maybe added subsequently.

To facilitate formation of the underlay 40 and "proper location of the details, it is preferredto' build up the details on a printed impression of the subject matter involved. If, as illustrated in Figs. 3 and 7, the details are to be added after the impression has been attached to the flat back surface 29 of themold, an offset proof 43 is taken from the original form 23 preferably on manila paper and cemented, printed side outward, onto the back of the mold with the different printed areas located with the aid of calipers or the like in proper register with the corresponding parts of the mold surface. The indentations 4| corresponding to the solid areas are then formed and located by taking a second offset proof 44 on paper of the required thickness and cutting out the proper parts so as to leave indentations of the proper depthwhen the second proof is pasted onto the first one with the corresponding parts in proper register. Then, the patches 42 are cut out from additional proofs or plain paper and pasted on the proof 44 or directly on the proof 43 in'case there are no -solids to be emphasized. By building up the make-ready de tails on the separate proof 43, location of the details regardless of their shape is facilitated.

The cost of the make-ready treatment can be reduced still further by building up the underlay 40 as a separate unit in a spec'al department of the printing shop. To this end, a direct proof Bl (Fig. 12) is taken from' the original 23 on heavy manila paper. A second similar proof 48 cut out to form the indentations 4i corresponding to the solid areas is then pasted onto the proof 4'! with register. Then patches 42 are added for the high light areas. The underlay thus formed is trimmed to the proper size so that when its edges are .matched with those of the mold 24 with the patches 49 lying against the back surface 29 of the mold, the printed parts wili register accurately with the corresponding cavities of the mold. In the assembly of the parts for the molding operation, an underlay of this character would be placed printed side up on the lower press platen 3i and the mold laid thereon as shown in Fig. 8, these parts being retained in proper matched relation by the bearers 35 or other suitable guides.

The method above described for treating the plates to incorporate make-ready therein automatically in the molding operation is especially advantageous in that it avoids individual treatment of the several plates whch are ordinarily As a. result,

the printing surfaces from ready details located the corresponding printed parts in By constructing and molding printing plates as above described, itwill be observed that a high degree of accuracy may be obtained in spacing the back of the carrymaintaining true parallelism therewith Owing to the thinness of the sheet and the resin layer in which the types are molded, the plate possesses sufficient flexibility to respond, under the pressure used in printing, to makebetween the sheet l2 and the backing plate 51,18. In this way, any additional corrections that may be required to make the plate ready for printing may be applied readily.

Where the printing plate is to be used for prolonged runs in the printing press, it is sometimes desirable to provide a printing surface which is more resistant to wear and the action of the inks than a surface composed wholly of the synthetic resins now available. To adapt the plate for such severe use, the surface of the plate including type projections in the resin layer H may be covered with a (Fig. 11) approximately .005 of an inch in thickness. This may be of any metal desired such as chromium electrodeposited on the mold 24 prior to the molding operation which is carried on without removing the shell from the mold, the parts first being arranged as shown in Fig. 10 after which the heat and pressure is applied in the manner above described. After molding, the plate assembly is stripped from the mold and the side edges 46 of the shell bent around the flanges 20 to form a unitary plate which may be attached to the press cylinder in the same manner as the resin surfaced plate first described.

I claim as my invention:

ing sheet l2 and in thin metallic shell 45 1. For use in reproducing from an original type sheet over said layer with a parting medium interposed therebetween to expose said material to areas of said sheet corresponding in size and shape to the type indentations in said mold, applying pressure to said mold and carrier sheet whereby to cause setting of said material with the molded type areas onhr adhering to said carrier sheet, and stripping ofi said parting medium and the material adhering thereto.

2. Themethod of making a printing plate reproduction of an original form type surface which comprises forming a mold from said type face, making a printed proof of said form on a paper sheet, cutting out the printed areas from said sheet, applying a layer of resin ingredients to the indented face of said mold, placing said paper sheet on said resin layerwith the cut-out portions matching with the corresponding type areas of said mold, heating said resin layer to a molding temperature, and pressing said resin layer and said proof sheet between said mold and a carrier sheet whereby to cause only the resin opposite said cavities to adhere to said carrier sheet, and stripping ofi said paper sheet and the resin adhering thereto.

3. For use in making a printing plate comprising a molded resin layer on a sheet of metal having a surface treated for the adherence of plastic resin thereto, the method which comprises forming a metal surfaced mold having cavities therein corresponding to the type to. be molded, masking the portions of said treated surface correspon to the non-type areas of said mold, covering the face of said mold with a layer of resin ingredients, locating said sheet with the exposed treated surface thereof in register with the type areas of the mold, pressing said mold and sheet together with said ingredients heated to a molding temperature, and stripping the resin off from the masked areas of said sheet.

4. For use in making a printing plate comprising a molded resin layer one sheet of metal having a surface treated for the adherence of plastic resin thereto, the method which comprises forming a metal surfaced mold having cavities therein corresponding to the type to be molded, masking the portions of said treated surface corresponding to the non-type areas of said mold, and pressing a layer of resin ingredients between the face of said mold and said sheet whereby to mold the type on the exposed areas of sheet.

5. The method of forming a printing plate which comprises forming a mold having cavities therein corresponding to the type to be formed, covering the face of the mold with moldable material, covering said material with a. carrier sheet having selected portions thereof corresponding to the type areas of said mold adapted for the adherence of the molded material thereto, and the remaining areas adapted for the nonadherence of the molded material and molding said material in said mold under pressure.

ARTHUR B. DAVIS.

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