US1696596A - Resistance unit - Google Patents

Description

Dec. 25, 1928.

C. DANTSIZEN RES ISTANCE UNIT Filed April 5, 1926 Figi.

Inve ntor: ChritLan DrtSLzQn. D 9 211;. .M

Patented Dec. 25, 1928.

UNITED STATES PATENT OFFICE.

CHBISTIAN'DANTSIZEN, OF SCHENECTADY, NEW YORK, ASSIGNOB T0 GENERAL ELEC- TBIC COMPANY, A CORPORATION 0F NEW YORK.

RESISTAN CE UNIT.

Application tiled April 5, 1926. Serial No. 99,778.

The present invention relates to conductors of high resistivity and more particularly to such conductors which are commonly emloyed in connectionxzith vacuum tubes and known as grid leaks. Resistance elements of this type have been made by drawing lines on paper, b spraying or painting porcelain or glass Wit ra hite and by various other well known met o s. Such resistances, however, usually have a serious disadvantage in that they vary in conductivity from time to time. The paper resistor, for example, is somewhat unstable, due to the fact that the cellulose fibers are hygroscopic or aiected by light, and in the very slight movements of the resistor unit the la er of conducting material is easily disturbe and its conductivity there? by chan d. Likewise, when resistance units are ma e by spraying or painting, it is difiicult to obtain uniformity in the value of the resistance.

In accordance with my invention, the resistor comprises an anhydrous material such as a lass rod having an etched surface, and provided at the end portions thereof with a ayer of conducting material. Lines are drawn on the etched surface of the glass rod and from end to end thereof with a carbon pencil until enough carbon has been rubbed on to the roughened surface of the glass to provide a resistance element having the de-V sired conductivity. Resistance elements constructed in this manner are practically constant in value and remain so throughout the life ofmthe f The accompanying drawing illustrates in Fig. 1 a glass rod from which sections may be cut to provide the resistance units; Fig. 2 is a perspective view illustrating the method of applying a conducting surface to the glass rod; while Fig. 3 is a cross sectional view i1- lustrating the completed resistor unit.

In carr ing my invention into effect, a glass or other suitable insulator rod 1 having a diameter of approximatel one-eighth inch is di ed into a solution o acid ammonium fluori e for a period of approximately 30 seconds in order to etch or roughen the surface of the rod. The rod is then Washed and dried, and cut into suitable lengths 2, as indicated in Fig. 1. Conductors 3 and 4, which ma be made of 20 mils Dumet wire, are then sea ed into the opposite. ends of each rod 2 and the ends of the` rod ofthe adjacent end portions of the conductorsare given surface conducting coatings, asindicated at 5 and 6. The `coatings may comprise, for example, a graphite composition known as aquadag, and Iunderstand this term to desi ate suspensions of graphite of colloidal eness in water. Coatin s 5 and 6 are of relatively high conductivity.

The rod 2 is now supported between clips, as indicated at 7 and 8 in Fig. 2. A sourcevof energy, such as a batte and a milliammeter, neither of whichare s own on the drawing, are then connected in series with the wires 3 and 4. AWhile thus connected a graphite or carbon pencil 9 is drawn from end to end of the etched glass rod 2 until suilcient conducting material has been rubbed on to the roughened surface of the glassto give a milliammeter reading corresponding to the quotient of the applied voltage and the desired resistance. The resistance element is then sealed into a glass tubeor container 10, as

- indicated in Fig. 3.

In`tl`ie use of grid leaks for radio sets, it is important that vthe resistance element show as little high frequency variation as possible. This property is particularly desirable bef cause variations in the resistance ofthe grid leak are transmitted through the detector and amplified by the succeeding amplifying tubes thus giving rise to scratching or distortion in the resulting signal. I have found by numerous tests that the type of grid leak which I have described shows little or no high fre"- quency variations and that, as a result, there is practically no distortion n received signals arising from the use of this form of resistant element.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A method of constructing a resistance unit which comprises etching the surface of a rod of vitreous material, sealing conductors into the ends of the rod, ap lying a conducting coating to a ortion oi) said conductors and to the ends o said rod, and drawing one or moreconducting lines on the roughened vitreous surface to electrically connect said conducting coatings.

2. A conductor comprising a rod of vitreous material having a roughened surface, a pair of wires sealed into o posite ends of the rod, the ends of said rod eing provided with a .surface layer of conducting material in contact with said wires, said roughened surface -being -provided with a deposit of conducting material connecting said surface layer.

3. A conductor comprising a lass rod having an etched surface, a pair o wires sealed into opposite ends of the rod, a surface layer of conducting material on each end of said rod and in contact with said wires, the etched surface of the rod being provided with one or more conducting lines connecting said sur- 10 face layers.

4. The method of constructing a resistance Legame unit,` which com rises roughening the sur- 'face of a rod o vitreous material, sealing` conductors into the ends of the rod, applying a conducting coating to a portion of said conductors and to the-ends of said rod, and drawing one or more conducting .lines on the roughened vitreous surface to electricallyl connect said conducting coatings.

Inwitness whereof, I Ahave hereunto set. 20

my hand this 2nd day of April, 1926.

CHRISTIAN DANTSIZEN.-

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