US2512347A - Dielectric stencil - Google Patents

Description

June 20, 1950 A. R. LINDSAY DIELECTRIC STENCIL Filed Sept. 25, 1948 V//MWM// l7 JN V ENTOR.

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Patented `une 20, 1950- DIELECTEIC STENCIL Allen R. Lindsay, Cleveland Heiglts, Ohio Application September 23, 1948, Serial No. 50,757

4 Claims. (CI. lol- 1282) This invention relates to a dielectric stencil for use with an electrical etching device such as is used for marking various types of metallic articles such as tools, machines and various parts thereof.

In devices of this kind the stencil has portions thereof depressed in the form of the character desired. The stencil is then secured to a suitable etching tool and in operation the stencil is brought into contact with the work to be marked and the depressions are filled with a suitable elec- Then an electric current is passed through the electrolyte to the work, the stencil holder or tool acting as the cathode and the work constituting the anode. Such an etching tool is shown in my co-pendng application Serial No. 631A01, filed November 28, 1945, and now issued as Patent No. 2,498,129 granted Sept. 2, 1949. The actual etching time is very short, just a few seconds, so that a very large number of articles a;

can be marked in a short time. As the stencil is repeatedly brought into engagement with the work, which very often has a rough surface, it quickly wears out and has to be frequently replaced which consumes considerable time and many stencils.

The principal object of the invention is to provide a dielectric stencil for use with electrical etching devices that is so constructed that it will have a much longer life and can be used a great many more times than previously known stencils of this character.

Another object of the invention is to provide a stencil of this character which will produce a clear-cut, well-defined mark upon a metallic article.

Another object of the invention is to provide a stencil possessing the aforesaid characteristics which is easily and economically manufactured and is very efcient in operation.

Other and more limited objects of the invention will be apparent from the following specication and the accompanying drawings forming a part thereof wherein:

Fig. 1 is a side elevation of a stencil constructed according to my invention;

Fig. 2 is 'a bottom plan View thereof; and

Fig. 3 is a greatly enlarged fragmentary section taken on the line 3-3 of Fig. 2.

Referring now to the drawings by reference characters, the numeral l indicates generally my improved stencil which as illustrated herein comprises a bottom 2 and an annular wall 3 integral with the bottom 2. The upper end of the annular wall 3 is fiared outwardly as indicated at 4. The

character to be etched is indicated at 5, which as illustrated is the numeral I. Although I have illustrated my improved stencil as generally circular in shape, it will be obvious to anyone skilled in this art that it can be square, rectangular or any other desired shape depending on the character .and. shape or size of the mark desired and on the type of etching tool With which the stencil is to be used. Also the stencil need not be cup shaped as shown. In some instances it may be desirable to have the stencil in .the form of a flat sheet.

The stencil is made from a composite sheet of material 6 which is first molded into the desired shape, after which the desired character is pressed into the bottom 2 by a suitable die.

The material 6 comprises a treated paper sheet i, a thin film of wax 8 and a thin layer of high temperature paraflin and buna rubber 9 all firmly bonded together into a composite sheet. The

paper 'I is preferably uncoated long fibre paper having extremely open tissues, which has been treated with chlorinated oil to seal the hygroscopic fibres and bond them together. The paper is very pervious so that electrolyte can readily pass through. A wax solution is applied to one side of the paper by passing the paper over a chilled roller which clips into a bath of the heated 'wax solution. The wax solution comprises parafin and beeswax, or other animal wax, which have been dissolved in ether or other suitable solvent and heated to approximately F. When the solution cools and dries, it forms the thin wax film 8 which is firmly bonded to the paper l. An emulsion of high temperature paraffin and buna rubber is then spray coated on the film of wax 8 by a hot blast air gun. As the emulsion comes into contact with the wax film 8` it solidifies forming the outer layer 9 of the stencil material 6. In preparing the paraffin and buna emulsion F. parafiin is melted and dissolved in mineral ether and then heated to approximately 200 F. The buna rubber is dissolved in acetone and ether, and then the hot parafin solution is added progressively in minute quantities to the buna solution while the buna solution is being Violently agitated. This produces a stable creamy emulsion.

After the stencil has been molded to the desired shape the desired character is impressed therein by forcing a suitable die into the outer face of the stencil. As the die is forced into the material it ruptures the buna film 9 and displaces the wax and buna films 8 and 9 and compresses the paper 'I as indicated at ID in Fig. 3. The dis- 'placed buna and wax films form a. raised border around the character as indicated at H. As the die is pressed into the composite sheet 6 to form the desired character the buna film 9 is first ruptured and the waX film is softened. Further pressure displaces the wax film 8 and the buna film 9 from under the die, leaving the paper sheet 1 eXposed as shown in Fig. 3. The pressing of the die into the composite sheet also compresses, but does not rupture, the paper sheet 'I forcing out ali oil and Wax from under the compressed portion thereby providing a section through which electrolyte can readily pass. If the wax film 8 was not provided between the paper sheet 'l andthe buna film 9 it would be very difiicult, if not impossible, to r-upture and displace the buna film r The First,

uncoated long fibre open tissue paper which has been treated with chlorinated oil to seal the hygroscopic fibres and bond them together, a film containing animal wax bonded to the outer side of said sheet, a second film containing synthetic rubber bonded to said first mentioned film, an impression in said sheet defining a character to be etched, said films being perforated by said impression, and said second film being displaced to provide a raised border around said impression.

2. A dielectric Stencil comprising a sheet of uncoated long fibre open tissue paper, a film containing animal wax bonded to the outer side of said sheet, a second film containing synthetic rubber bonded to said first mentioned film, an

- impression in said sheet defining a character to it helps to strengthen the paper sheet 1, which in its natural state is veryweak; and second, permits the rupturing and displacement of the buna film 9 without rupturing the paper sheet 1. After the character has been impressed in the Stencil the depression is filled with electroiyte and an electric current is passed through the electrolyte. This generates enough heat to cure and yulcanize the rubber film forming the 'Walls !2 of the depression and the raised border ll therea'ound. This gives the rubber high mechanical strength and provides a tough tenacious film which resists mechanical abrasion. The curing of the rubber film is generaily accomplished by attaching the Stencil to an etehing tool and using it once `or twice to mark some .article.

In practice it has been found that a `Stencil constructed in this manner can be used 1900 times before it is worn beyond :a desirable usage point.

Other known stencils when used in the same manner averaged only 30 times.

From the foregoing it will be apparent to those skilled in this art that I have provided a Very simple and efiicient device for accomplishing the objects of my invention.

It is to be' understood that I am not restricted `to the particular construction shown and described herein as various modifications can he 'made therein within the scope of the appended claims.

Having .thus described my invention, I-- claim:

1. A dielectric Stencil comprising a' sheet of rubber bonded to said first mentioned film, an

:impression .in said sheet defining ta character to be etched, said .films being perforated by said impression.

4. A dielectric .Stencil 'compri sing ;a sheet of uncoated long fibre open tissue paper, a :film containing 'animal waxbonded to the outer side of said sheet, a .second. film containing synthetic rubber bonded .to said first mentioned film, an impression in said .sheet defining a .character to be -etched, said films being .perforated by said impression.

ALLEN R. LINDSAY.

CES CITED The foliowing references 'are of record in th file 'of this patent:

UNITED STATES PATENTS 'Number Name Date 1,293,983 Thomas Feb.. 11, 1919 1,37,1.57 Gestetner i VMar. 8, 1921 1 633972 Davis June 21, 1927 2,'14O,5D6 aGanning Dec. 20, '1938 &405,-508 Lindsay .Aug. 6, 19446

Claims (1)

1. 4. A DIELECTRIC STENCIL COMPRISING A SHEET OF UNCOATED LONG FIBRE OPEN TISSUE PAPER, A FILM CONTAINING ANIMAL WAX BONDED TO THE OUTER SIDE OF SAID SHEET, A SECOND FILM CONTAINING SYNTHETIC RUBBER BONDED TOS AID FIRST MENTIONED FILM AN IMPRESSION IN SAID SHEET DEFINING A CHARACTER TO BE ETCHED, SAID FILMS BEING PERFORATED BY SAID IMPRESSION.

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