US2255440A - Electroforming method of preparing stencils - Google Patents

Description

w. R. SHERMANV Filed Feb. 2o, 1939 Sept. 9, 1941.

ELECTROFORMING METHOD OF PREPARING STENCILS Patented Sept. 9, l149,41

s PATENT. OFFICE LECTROFORMING lVIETHOD F PREPAR- ING STENCILS Wilson R. Sherman, Fall River, Mass. Application February 20, 1939, Serial No. 257,324

3 Claims.

This invention relates to printing stencils, and in particular to a printing stencil of the type used for printing on or decorating sheet material, such as paper, fabric, etc., which may or may not be fed asa continuous web past the stencil, and has for one of its objects printing, stencil and a simple and inexpensive method cfmaking the same.'

to provide an improved Another object of the-invention is to provideL the holes constituting printed are formed a printing stencil in which the design or pattern to be Y without mechanically punching out the material of the stencil.

, Another object of the invention is to provide a. method of forming a stencil in which the complete stencil including the holes forming the design or pattern to be printed will be produced at the same time and during electro-deposition of a deposit of metal upon conductive surface portions of a support carrying non-conductive areas in the pattern desired to be holes in the nal stencil.

With these and other objects in view, vention consists of certain novel features of -construction, as will be more fully described, and particularly pointed out in the appended claims.

In the accompanying drawing:

Fig. 1 is a side elevational view of a seamless cylindrical printing stencil made in] accordance with my invention;

Fig. 2 is a central longitudinal sectional view taken on the line 2-2 of Fig. 1 showing one feasible method by Fig. 3 is a fragmentary view of the matrix, in flat form, ready to be shaped into cylindrical form and mounted either within or over a cylindrical support forareceiving an electro-deposit of metal which is to be the final stencil;

Fig. 4 is a transverse sectional view taken on the line iof Fig. l;

Fig. 5 is a. central longitudinal section View similar to Fig. 2 but differing therefrom by depicting the final stencil as being produced upon the exterior cylindricalsurface of the cylindrical support;

Figs. 6, '1, 8 and'9 are diagrammatic sectional views illustrating the various steps of my preferred method of making a printing stencil;

Figs. 10, l1, l2 and 13 are sectional views illustrating diagrammatically the various steps in carrying out a modied method of making a printing stencil Figs. 14, 15, 16, 17 and 18 are diagrammatic sectional views illustrating the various steps in which the stencil may bel produced within a hollow cylindrical support;

the ing carrying out another modied process ofv making a printing stencil; and

' Fig. 19 is a vertical sectional view diagrammatically illustrating one form of electro-plating process for producing one of the printing stencils in which the stencil and the anode are outside the support carrying the stencil.

Printing stencils such as those of the type now employed for fabrics, paper, and various sheet'materials, which may or may not be supplied incontinuous lengths', usually consist of a thin walled hollow copper cylinder, the entire cylindrical surface of which is perforated by small holes arranged to form the desired pattern or design to ,be printed. At present such stencil rolls are usually made by taking a piece of sheet metal stock in at form and punching out the holes to form the desired pattern by means of suitable dies. The perforated sheet, thus formed, is then bent into tubular or cylindrical shape, after which the abutting side edges are united, as by being suitably brazed, welded or soldered to securely hold them together. Such a construction, however, is not entirely satisfactory since it produces an objectionable seam, the avoidance of which requires the careful locating of the design to be applied on the cylinder. In many instances, this difficulty cannot be overcome and since the seaming cannot be machine punched without causing possible injury to the seam it has been necessary to cut out such portions by hand. As to the procedure of making such a stencil cylinder by a machine punching operation, such a process has been very costly owing to the fact the individual parts of each figure of the pattern, which are to be holes in the i'lnal stencil, necessarily have to be separately a cutting element on the diethat is capable of v reproducing some of thedelicate forms of perforated patterns because of the design and di- 'mensional limitations of various cutting portions of the die necessary to insure the proper strength and cutting action thereof on the sheet metal stock; and in order to overcome the aforementioned disadvantages and to provide a simple and relatively inexpensive process whereby a printing stencil may be produced. either as a seamless cylinder or in substantially flat sheet printing patterns on or decorating' form, in which the arrangement of holes forming the pattern or design required to beprinted are produced without the use of stamping or. punching dies, I have provided a process wherein the entire stencil including the holes therein, which form the pattern or design, is produced electrolytically; and I produce these holes by initially preparing a surface of a support so as to provide Aelectrically conductive portions thereon interrupted by or interspersed with other portions `which are electrically non-conductive, the arrangement of such non-conductive portions being Figs. 2, 3 and 5 for making a cylindrical printing stencil, in which the foundation member- 22 is preliminarily preparedA separately from the support 28 and consists of a piece of sheet material, such as paper or other suitable thin flat material, on which there is carried .an exterior layer of wax which is suitably applied thereto, as by impregnating or coating the sheet material.

Applied to said wax surface of the foundation.

member 22 is a thin layer or coating of graphite or a metal powder to provide the conduct-ing surface 2|, the graphite or powdered metal being dusted over the entire outer surface of the foundation vmember 22 intended to receive the re- Insofar as the practice of the present inventionis concerned, it is to be understood that the invention is applicable in whole or in its several aspects to the production of printing stencils of any desired shape, such as, for example, in the form either of a thin hollow cylinder or as a substantially flat sheet. In the embodiment which I have shown in the drawing, Figs. 1, 2, 4 and 5, and chosenbecause of its simplicity of representation for illustrating -one feasible process for making one of the printing stencils, the stencil is there shown in the form of a thin hollow cylinder or shell 20, which is produced by the electro-deposition of a layer of some readily palatable metal, such as copper, on electrically conductive surface portions 2| of a suitable matrix carried by a support 28 which may be either a hollow or a solid body, and made either Y, of a metallic or of a non-metallic material. As

illustrated in Figs. 2, 3 and 5, the matrix used in this method consists of a foundation member -22 made of an electrical insulating material,

preferably a composition of relatively low fusibility, such as parailln or..other suitable wax or waxy material, or any non-conductive material of low melting point which will permit the exterior layer 20 of electro-deposited metal forming the required stencil to be readily stripped from the support 28 by heating suchv non-conductive material ofA low fusibility to soften or melt the same, and at a temperature of a lower degree than the melting point of the material which forms the support 28.

'While it is feasible that the foundation member 22 can assume the form of a wax coating directly applied on either the inside or on the outside of the support 28 various difficulties are encountered that render this method impracticable, particularly where the design or pattern desired to be reproduced is to be applied to such a coating if the same is located inside of the support 28. In actual practice4 it is preferred to produce the'cylindrical printing stencil on the inside of a hollow cylindrical support since the final stencil member when thus formed' will be found to have a much smoother exterior cylindrical surface bettersuited for direct contact with the material to be printed than would be produced if the stencil were formed on the outside of the support where the inside peripheral surface of the stencil, and not the outside, would be next to the conductive surface 2|. To this end, I employ a matrix of the character shown in the present illustrative process represented in quired layer of electro-deposited metal forming the shell 20. I then coat portions or areas 26 of the outer surface of the electrically conductive surface 2|, thus formed, with a material incapable of conducting electricity and applied in the design or pattern which are to be holes in the final stencil, such as, for example, the holes 23, 24 and 25, as shown in Fig. 1. By making the matrix as described above, the holes which constitute the required perforated design or pattern in the final stencil cylinder will be produced electrolytically during theA subsequent electro-plating process hereinafter to be described for electro-depositing the metal layer to form the shell 20, said -holes being produced by reason of the non-deposition or non-adherenceof the plating metal'upon the electrically non-conductive areas26 which interrupt the continuity of the conductive surface 2| and are carried by the conductor surface at locations thereon corresponding to the design or pattern arrangement intended to be reproduced. To this end, the non-conductive areas 26 are made of a suitable electrical insulating material, such' as asphalt or a casein paint, which is applied as a surface coating to cover portions of `the electrically conductive surface 2| in the same pattern and at locations thereon which are to be the holes desired to be produced in the final stencil. The electrically non-conductive coatings 26 may be applied to the conductor surface 2| in any suitable manner, such as by a printing process, or by being painted thereon with or without the use of a stencil, or by spraying the coating material through a stencil,'the manner of application being readily effected by reason of the ilat form of the foundation member. The complete matrix, thus made, may be -either wrapped around the exterior-surface of the cylindrical support 28, as indicated in Fig. 5, or it may be rolled into cylindrical form and inserted inside the hollow cylindrical support 28 as shown in Fig. 2in which instance the circumferential length of the rolled sheet being such as to enable the sheet to fit closely against the inner peripheral surface of the hollow support 28 to completely cover the same and also expose complete hole patterns or designs. The support 28 thus prepared with the matrix is then suspended Within a tank containing a suitable electrolyte, such as copper sulphate, and by the action of electric current an Aelectro-deposit or plating of copper to the thickness desired is deposited lby the usual electro-plating process on the portions of the electrical conductive surface layer 2| that are not covered by the insulated coatings 26.

In Fig. 19, I have illustrated diagrammatically the electro-plating process in whicha support 28 with the matrix mounted, on the outside thereof, is suspended in the plating bath containing an electrolyte solution E, a metal anode of the metal to be plated, such as copper, and source of electric current C in order to produce le metal deposit by electro-deposition. In this stance, the stencil cylinder is produced electrotically on the outside of the support and the iode 29 is disposed exteriorly of the support. Iowever, when the stencil cylinder is to be )rmed inside of the support 28, the anode 29 ien will be disposed within the hollow support, nd the electro-plating process will be carried ut inthe general manner as just described above i obtain the desired deposit of the plating metal. 'he deposited metal layer 20, thus formed and 'hich constitutes the vfina-l stencil cylinder, may hen be removed from the support 28 when the equired thickness of the plating is obtained hereon, by melting or softening the wax layer 2 to an, extent sufficient to effect separation of he metal layer 20 from the support 28. In the mbodiment illustrated i'n Fig. 5, the metal deosit 20 is shown as being formed over the outide of the support 28, thus distinguishing in this articular from the .process just described in :onnection with Figs. l to 4 inwhich the iinal ltencil is shown as beingproduced within the iupport 28. In -other words, the metal deposit l is produced in the same manner as the formation of the layer 20, above described, and the varocess steps utilized to obtain electro-deposition 3f the metal may be the same as those described 'Ln connection with the formation ofthe stencil within the cylindrical support 28 except that the wax layer 22 carrying the layers 2l and 26 is Wrapped around the exterior surface of the cylinder 28 instead of being placed inside thereof as in the previously described embodiment shown in Fig. 2. If desired, the outer surface of'the cylinder 28 may be coated with a layer of wax and the conducting layer 2l and -the insulating coating 26 applied in succession thereto.

In Figs. 6 to 9 inclusive, I have illustrated diagrammatically my preferred process in which I first prepare a base 0r support 30, which may, be in the form of either a sheet or as a solid, or as a hollow cylinder, and made either of a metal or a non-metal, with an outer surface coating 3| of wax upon the top surface of which is then applied coatings 32 of a material which is a nonconductor of electricity and arranged in the design to be holes in the final stencil. The coatingsv 32 may comprise a suitable paint, such as a casein paint, which is susceptible to attack by suitable chemicals or soluble in a liquidI such,as for example, water. The entire body including the whole surface with the painted design is then coated with a coating 33 of graphite or a metallic powder to form an electrical conducting surface and the body then immersed into a liquid of a character capable of acting on the paint to remove the surface of the paint to release the graphite or metal powder attached thereto at such locations, thereby destroying the electrical conducting surface 33 of the sheet or solid at the coated areas so that during subsequent electroplating of the sheet or solid by the usual electroplating process, the layer 35 of plated metal, such as copper, will be deposited only where the graphite or powder is present. When the desired thickness of plated copper is obtained, the support 30 isf then removed from the plating bath and the metal layer 35, which may be of cylindrical shell-like shape, separated and removed from the support byv melting the wax layer 32.

In Figs. to 13 inclusive, I have shown a different modified process for providing a stencil, in which I rst provide a base 40, made of v material of low fusibility such as wax, in a sheet or a solid form, with a layer 4I of an electrically conductive material, such as graphite or a metal powder, to which I then apply on parts of the outer surface of the layer 4I, a coating 42 which is arranged in the same pattern or design which are to constitute the holes in the final stencil, and applied ina. suitable manner, such as by being printed or painted on the outer surface of the layer 4I with a substance which willA resist electro-deposition of metal, such as asphaltum or a lacquer. The sheet vor solid, thus prepared, may then be immersed into an electroplating bath containing a solution of copper sulphate as the electrolyte, the composition of which may be that usually employed in the art of copper plating, and the desired thickness of an electro-deposit of copper deposited on the portions of the sheet or solid uncoated with the resist coating 42. The electro-deposited metal layer 43,` which is the nal stencil, may then be separated from the base in any desired manner, such as by melting or softening the wax base 40 to permit the metal deposit 43 to be peeled off or disconnected successfully.

In another modified process, as represented in Figs. 14 to 18 inclusive for electrolytically producing a stencil, I first coat a base 50 in the form of a sheet or a solid, which may be either a metallic or a non-metallic material, with a layer 5I of wax after which the outer surface of the wax coating is dusted with graphite or a metallic powderto provide an outer electrical conductive coating 52. The metal coated product, thus formed, may then be subjected to treatment in a copper plating bath on which a thin "fiasliing or layer 53 of copper is electro-deposited over the graphite or metal powder coating 52. This deposit or ashing" layer 53 may then be covered with the resist coating 55 of paint, such as asphalt, or a varnish, or -a lacquer, in the desired arrangement of pattern or design where it is desired that holes appear in the finished stencil. The laminated body may then be immersed in a' copper plating bath and the electroplating operation carried out lfor a sufcient time to build up the desired vthickness of copper to form the layer 56 with the arrangement of holes appearing at positions where the pattern is required and which will be the final stencil. Where the required thickness of metal deposit is obtained, the metal layer 56 forming the final stencil may then be detached from the support by heating the wax coating 5I after which the thin iiashing layer 53, at the points covered by the resist paint coating 55 is applied, may be removed by disrupting the thin asliing in a suitable manner, such as by a harsh brushing operation to break out the holes so that there will remain the complete holes through the stencil arranged in the design which is required.

The foregoing description is directed towards the methods and constructions illustrated, butI desire it to be understood that I reserve the v privilege of resorting to alll the equivalent changes to which the constructions and methods Iare susceptible, the invention being defined and limited only by the terms of the appended claims.

I claim:

1. The method of producing a printing stencil comprising the steps of providing a base having a waxed surface, coating portions of the waxed surface of said base with a material which is soluble and removable from said waxed surface by being dissolvedtherefrom, said coatings forming areason the waxed surface corresponding to the -desired pattern and at locations which are to be holes in the final stencil, covering the whole of said 'exposed ywaxed surface of the base and also the surface of said soluble coatings with a metallic material which is a good conductor ofelectricity and in a finely divided state, then removing said soluble coatings from the waxed surface of the base by treatment with a liquid ofY a character capable of dissolving said soluble coatings and which does not dissolve the waxto release the finely divided electrically conductive material attached thereto and leave areas of wax exposed to view in the conductive metallic layer at the locations formerly occupied by said soluble coatings and at locations which are to be holes in the final stencil, electrically depositing a metal on `the metal coated surface of the base to form the final stencil, and then Aremoving the electrically conductive properties, removing saidvv casein. coatings from said waxed surface bythe action of a liquid of a character capable of acting on casein paint to destroy the same and release the metal powder on the surface of the casein but which does not act on the wax to thereby leave areas of wax exposed to view in the conductive metal layer at .portions thereof formerly occupied by said casein paint andI at locations which are to be holes in the final stencil, then electrically depositingA copper on such metal surface of the base to form the final stencil and then removing the deposited metal from said base.

3. The method of producing a printing stencil comprising the steps of providing a support having a waxed surface, coating portions of the waxed surface of said support with casein paint, said coatings being applied to areas on the waxed surface corresponding to the desired pattern and at locations which are to be holes in the final stencil, covering the whole of said exposed waxed surface of the support and also the surface of said` casein-coated areas with powdered graphite to provide an electrically conductive surface, removing said graphite-coated casein areas by dissolving the same with a material in which the wax is insoluble to disrupt the continuity of said conductive surface and leave openings therein exposing to view the wax-coated surface of the support at the locations formerly occupied by said casein material and corresponding in design to -the pattern arrangement desired to 4be pro- .duced as holes in the final stencil, thereafter f electrically depositing copper upon the graphitecoated portions of said support and then removing the deposited metal from the base.

WILSON R.' SHERMAN.

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