US2994848A - Resistor device - Google Patents

Description

Augl, 1961 v c. c. RAYBURN 2,994,848

REsIsToRDEvIcE Filed Aug. 20, 1958 n@ Za 8.

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7 (d) 5 Q0 24 4 c HARLES L. RAY/Bmw United States Patent O 2,994,848 RESISTOR DEVICE Charles C. Rayburn, Falls Church, Va., assignor, `by mesue assignments, to Illinois Tool Works, Chicago, Ill., a corporation of Illinois Filed Aug. 20,1958, Ser. No. 756,148 10 Claims. (Cl. 338-328) This invention is in a resistor which is adapted by versatility of design and construction to provide available combinations of resistive values and which is adapted to the manufacture and fabrication of miniature circuit components.

In miniaturization of circuit components for applications, in which the available space is greatly limited, it has been the practice to use types of printed circuitry, as well as modular construction of the circuitry. Resistors and capacitors have previously been formed as coatings on insulated supports, which in tum are assembled to forrn portions of the desired circuit. In miniaturizing a circuit, there is an advantage in being able to eliminate bulky parts and in providing circuit components,'which in themselves are of minimum size, but which readily lend themselves to Variations of their electrical values by simple changes in circuit connections only.

It is, therefore, an object of this invention to provide a novel resistor device, which isv readily adaptable to miniaturization techniques.

It is another object of the invention to provide a novel resistor device, which can provide various combinations of resistance values.

It is a further object of the invention to provide a resistor device of novel design, having versatility in the provision of available resistance values combinations.

The invention consists of a resistor device formed from a continuous strip of resistive material mounted on an insulated base. The resistive strip is normally formed with a central apertured portion. Conductive terminals are fixed to the resistor device in the form of strips of conductive material extending from the apertured central portion across the resistive strip, so as to divide the strip into segments. The conductive terminal strips may be connected into a circuit in various ways to provide combinations of the segments of the resistor strip in parallel and series arrangements.

FIG. 1 is an elevational view of a support member used in a resistor device, fabricated in accordance with the invention.

FIG. 2 is a plan view of a resistance element used in the fabrication of the device of the invention.

FIG. 3 is an elevational view of a resistor device in accordance with the invention.

FIG. 4 is a graphical representation of the characteristic of the resistance element in accordance with the invention.

FIGS. 5 through 12 are schematic representations of variations in the design of the resistor device, in accordance with the invention.

The resistor device, in accordance with the' invention, consists of an insulating support member on which is mounted a resistance element in the form of a plastic strip, coated with resistive material. 1 discloses a particular design of an insulated support member, consisting substantially of la square ceramic wafer formed of fired steatite. The wafer 10, shown in FIG. 1, is formed with a pair of notches 12 extending Specifically, FIG.

into each side of the wafer 10. As represented by the there are formedtourterminal `stn'ps.16, .whichare positioned so that each extends substantially from a diierent corner of the wafer radially toward the center.

Conductive strips 16, as well as the conductive coatings 14, may be of any appropriate material and, for example, may be applied as a liquid suspension of glass and silver particles in a volatile carrier. The conductive coatings in this form may be sprayed or painted on the desired surface of Wafer 10 and then baked to drive olf the volatile carrier and to fuse the conductive coating into the ceramic of wafer 10. As indicated by the dotted lines, the terminal strips 16 may, if desired be joined by a conductive strip 18 to the conductive coating 14 in any one of the notches 12,. This would enable the connection of any of the terminal strips 16 to a lead structure iixed in the respective notch 12, by soldering, for example.

FIG. 2 discloses a resistance element 20, which is used in accordance with the invention in the fabrication of the novel resistor device. The resistance element 20 is a strip of resistive material formed as an endless circular annular'strip enclosing a -central aperturey 22. The resistive strip 20 may -be fabricated from a carbon com position coated on the surface of a high temperature nonhygroscopic lm. Such a carbon coating, forming the resistance element, comprises powdered carbon mixed with an inert iller, such as, sodium silicate and a resin, as ethoxyline, which is a condensation product of epichlorohydrin with bis-phenol. One such a mixture comprises carbon 33%, ethoxyline resin 17%, and sodium silicate 50%. This mixture provides a total resistance of 2500 ohms between a pair of terminal strips 1A inch in diameter and spaced 3A; of an inch apart. The resistance can be greatly increased by lowering the percentage of the carbon and increasing that of the ethoxyline resin.

FIG. 3 discloses a resistor device in which the resistive element 2'0 is mounted on wafer 10 and bridging the spaced conductive terminal strip 16. Resistance element 20 is symmetrically placed on wafer 10 and is fixed thereto by baking the assembled parts at a temperature around 350 F., for va period of time between thirty minutes and one hour. The resistance element 20, during the baking procedure, -becomes tightly bound to the surface of ceramic Wafer 10, as Well as to the conductive strip 16.

FIG. 4 graphically discloses variations in the resistance ratio of element 20 with respect to changes in the external radius r of the circular annulus. The resistance ratio is the ratio of the resistance of a selector of strip 20 between any two terminal strips 16 when the inner radius ro of vannulus 20 is fixed at 0.050 inch and the outer radius is varied from 0.100 inch to 0.070 inch to the resistance of the same sector having an inside radius of 0.050 inch and an outside radius of 0.100 inch. The circular annular shape of resistance element 20 (FIG. 2) lends itself to being punched out from sheets of resistive material with the internal radius ro, kept xed, while the external radius r of the punch may be varied to provide resistance elements 20 of different size and value. Small variations in the outer radius r of punches of the sameV size vare not excessively critical in changing the resistance value of the element 20.

Since the resistance 20 is symmetrically positioned on the terminal strips 16, it is divided by the terminal strips into four sectors of equal area. In FIG. 3 the four terminal strips are also labeled A, B, Cand D and the area ofthe sector of element 20 between strips A and B is approximately equal to the `areas of the sectors between terminal strips B and C, C and D, and D and A respectively. If the resistance of the element 20 vbetween any two of the terminal strips is equal to R, it is then possible to provide resistor combinations having values in multiples of yR.A t

FIGS. 5 through 11 disclose dierent combinational arrangements of the terminal strips A, B, C and D with the resistive annulus 20. In FIG. 5 each of the terminal strips A, B, C and D are insulated from each other and in the manner shown in FIG. 1. FIG. 5a schematically shows the physical relationship of the terminal strips A, B, C and D and annulus 20, while FIG. 5b represents schematically the equivalent circuit for this arrangement. The total resistance across terminal strips A and B is equal to FMR, since the sectors between A and D, D and C, and C and B are connected together and are in parallel with that between terminal strips A and B. FIG. 5b illustrates the arrangement clearly. The resistance across the two diagonally disposed terminals A and C, for example, is equal to R, since these terminals are connected by two resistances in parallel and each equal to 2R,

FIG. 6 discloses a modification, in which terminal strips A and Care conductively connected. 'I'his may be done externally of the resistor device or may be done by forming terminal strips A land C as a single strip across the center of the annulus 20. This arrangement provides a pair of resistors AD and BC having a resistance of R/ 2, as well as a single resistor BD equal to R, as is indicated in FIG. 6b.

FIG. 7 discloses a modification, in which a pair of adjacent terminal strips A and D are connected together to provide the circuit arrangement disclosed in FIG. 7b. This arrangement provides a resistor equal to 2/3R, since the total resistance between A and B equals the inverse of the sum of l/R and 1/2R. As shown in FIG. 8, by connecting adjacent pairs of the terminal strips, a circuit arrangement is obtained in which the resistance values R/2 can be obtained.

FIG. 9 discloses an arrangement of the sectors of element 20, in which a plurality of resistors, each equal to R, may be connected to provide resistors having the values of R, 2R, and 3R, respectively. This is possible by breaking the resistance element 20 between any two adjacent terminal strips, such as indicated at 24 in FIG. 9a. 'Ihe circuit arrangement obtained is that disclosed in FIG. 9b.

In FIG. 10 resistance values of R are also obtainable, if the resistance element is cut on opposite sides, as indicated at 24 and 26 in FIG. 10a. This provides two separate resistors each equal to R, as indicated in FIG. 10b.

FIG. 1l discloses a possible arrangement, in which resistance element 20 is broken at 24 and terminal B and D are conductively joined. 'Ihe resultingcircuit arrangement is shown in FIG. 11b having a resistor equal to R between terminals A and B, a resistor equal to R/Q. between terminals B and C, and a resistor equal to 3R/2 between terminal A and C.

FIGS. 12a and b disclose other possible congurations of the resistance element. FIG. 12a represents a resistor element 28 formed as a hollow square, which is mounted symmetrically on four terminal strips A, B, C, and D. FIG. 12b represents a resistor in which the resistance element 30 is oval shaped with a similarly shaped central aperture and symmetrically positioned on the radially positioned terminal strips A, B, C, and D. All of the various combinations possible with the annulus resistance element 20 are also possible with the apertured configurations 28 and 30 of FIG. l2. That is the combinational arrangements disclosed, by Way of example, in FIGS. 5 through 11 are also possible with the resistance devices of FIG. 12.

I claim:

1. A resistor device comprising a support of essentially rectilinear configuration, a non-rectilinear continuous strip of resistive material on said supportand extending about and enclosing a portion of said support, a plurality of spaced conductive terminal strips on said support, each of saidI terminal strips extending Ifrom the corner `portions of said support portion across and in contact with said resistive strip, means conductively connecting two of said terminal strips together.

2. A resistor device comprising a support, a continuous strip of resistive material on said support and extending about and enclosing a portion of said support, a plurality of spaced conductive terminal strips on said support, each of said terminal strips extending from said support portion across and in contact with said resistive strip, two of said terminal strips being aligned with each other, a third one of said terminal strips positioned intermediate said two aligned terminal strips, conductive means connecting said two aligned terminal strips together.

3. A resistor device comprising an insulating support of rectilinear configuration, an endless strip of resistive material on one surface of said' support, said endless resistive strip being formed around and enclosing a central portion of said insulating support, a plurality of spaced conductive terminal strips on said insulating support and extending from said central support portion across and in contact with said endless resistive strip and therebeyond toward the corner portions of said one surface for electrical connection to a circuit.

4. A resistor device comprising an insulating support of rectilinear configuration, a strip of resistive material on said support, said resistive strip being formed around and enclosing a central portion of said insulating support, a plurality of conductive terminal strips on said insulating support, each of said terminal strips extending from said central support portion across and in contact with said resistive strip, said terminal strips being positioned to divide said resistive strip into a plurality of equal segments, and conductive means connecting two of said terminal strips together.

5. A resistor device comprising an insulating support, an endless strip of resistive material on said support, said endless resistive strip being formed around and enclosing a central portion of said insulating support, a pluralityof spacedconductive terminal strips on said insulating support, each of said terminal strips extending from said central support portion across and in contact with said endless resistive strip, said terminal strips being positioned to divide said resistive strip into a plurality of equal segments, and conductive means connecting together-an alternate two of said terminal strips.

6. A resistor device comprising an insulating support of rectilinear configuration, an annular strip of resistive material on said support, said annular resistive strip being formed around and enclosing a central portion of said insulating support, a plurality of spaced conductive terminal strips on said insulating support, each of said terminal stripsextending radially from said central support portion across and in contact with said annular resistive strip, said terminal strips being symmetrically positioned relative to said annular resistive strip to divide said resistive strip into a plurality of equal segments and for connection thereof With corner portions of said support.

7. A resistor device comprising a flat insulating support member of angular form defining spaced corner portions, notches formed in the marginal edges of said support at each side of each corner portion, said notches being formed with a conductive coating, a plurality of terminal strips mounted on the top of said supporting member, each terminal strip extending substantially inwardly from each of said corners of the supporting member and radially toward the center thereof, an annular resistor of strip material enclosing a center aperture mounted on said support and superimposed upon said terminal strips, said annular resistor having its inner and outer marginal edges spaced within the end extremities of each of said terminal strips.

8. A resistor device. comprising a support, a continuous strip of resistive material on said support and extending around and enclosing a portion of said support, a plurality of conductive terminal strips on said support positioned .between said support and said strip, each of said conductive terminalstrips being of substantially the same width and said terminal strips extending from said support portion across and in contact with said resistive strip and being symmetrically spaced and insulated from each other by said support.

9. A resistor device comprising a support having a substantially square configuration on at least one surface, a strip of resistive material on said one square sur-face of said support and extending about and enclosing a portion of said support, a plurality of conductive terminal strips on said support and beneath said resistive material, said terminal strips extending from at least some of the corner portions of said square surface of said support portion across and in contact with said resistive strip, two of said terminal strips being aligned with each other, and a third one of said terminal strips positioned intermediate said two terminal strips.

10. A resistor device comprising an insulating support of rectilinear conguration, a strip of resistive material References Cited in the file of this patent UNITED STATES PATENTS 2,474,988 Sargrove Tuly 5, 1949 2,632,831 Pritikin et al Mar. 24, 1953 2,717,942 Andrews Sept. 13, 1955 2,726,304 Gribble Dec. 6, 1955 2,859,315 Joerndt Nov. 4, 1958 2,864,924 Mayer Dec. 16, 1958

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