US2935712A - Multi-terminal non-linear resistors - Google Patents

Description

y 3, 1960 B. J. OPPENHEIM ETAL 2,935,712

MULTI-TERMINAL NON-LINEAR RESISTORS 2 Sheets-Sheet 1 Filed Feb. 4, 1958 b I /y am m MM M W F N fi R Z w N JMM Mr 5: 5% Y B y 1960 B. .1. OPPENHEIM ETAL 2,935,712

MULTI-TERMINAL NON-LINEAR RESISTQRS Filed Feb. 4, 1958 2 Sheets-Sheet 2 United States Patent MULTI-TERMIN AL NON-LINEAR RESISTORS Ben J. Oppenheim, East Orange, Meyer Sapoif, Union,

and Marsden Louis Miller, Mountainside, N.J., assignors to Victory Engineering Corporation, Union, NJ.,

. a corporation of Delaware Application February 4, 1958, Serial No. 713,175

2 Claims. c1. ass-40 This invention relates to a multi-terminal non-linear resistor of the type whose resistance varies considerably with the applied voltage. tors made of material whose resistance varies substantially with the temperature. The. invention also has par ticular reference to control and modulating circuits using the Inulti-contact resistors for application in communication and other controllable electrical circuits.

' The resistor units herein described are generally classified as thermistors and varistors. Both these types are generally made by sintering a composition .of resistor material into a desired shape. By choosing the composition of the resistor material, resistors may be fabricated which vary substantially with the applied voltage in the case of varistors or vary substantially with the temperature for thermistors.

Prior art resistors have been made by either forming the resistor material around a pair of conductors during the fabrication process, or else forming the resistor material into a suitable shape, firing a contact onto the surface and applying the conductors to the contact surfaces by means of soldering or brazing or by means of pressures. However, it was not heretofore possible to vary the resistance in such articles.

It has been found that the most satisfactory method of applying a contact to the surface of a non-linear semiconductor type resistor and especially to thermistors and varistors, is to deposit, spray, or fire a metallic or some electrically conductive coating onto the surface of the body. 7 This method produces a contact which reduces the extremely high contact resistance brought about by a direct application of the contact to the surface of the resistor. By applying a number of discrete coatings and then soldering or otherwise securing a lead to each coating, a number of resistance values may be obtained from a single rod, disk or washer shaped structure. Such multicontact resistors may be used in control and modulating circuits for a wide variety of electrical applications. They are also useful where precise values encountered during experimental development cannot be predetermined. In such applications, a broad range of experimental values can be used without removing the thermistor or varistor from the circuit. The user therefore has a convenient means to rapidly determine precisely what value is most advantageous for his circuit configuration. With the use of the herein described devices it is now possible to place a single unit ofmultiple values in an installation or test device or similar apparatus and make a large series of tests in a comparatively short period of time. Such a procedure would, in many cases, be impossible if individual units had to be installed and removed repeatedly to perform the same task. In the performance of a series of experiments to determine the suitability of a given thermistor or varistor resistance value, there are generally a large number of parameters which may vary during the course of the experiment, other than the resistance value of the thermistor or varistor which is intentionally varied.

It also relates to similar resis Since the variation of the other parameters may not be constant for each individual experiment, the results'obtained are sometimes confusing and misleading. Itis now possible with the use of the present invention to obtain I the interval of time required to change thermistor units to simulate the tests.

In utilizing thermistors or varistors,'circuit'requirements are such that it is often desirable to restrict the range of resistance variation obtained for a specified tem perature range or voltage range respectively to a narrow band without reducing the inherently high sensitivity of the component. In the past, this was accomplished by using several elements having different resistance values at a specified reference condition. In many applications space requirements prohibit the use of several elements. Also, when using thermistors it is often essential that the temperature measurement be restricted to a very small volume or preferably to a single point. In such cases, even when sufilcient space is available, the physical measurement loses all significance when, more than one element is used. With the use of the present invention, it is now possible, with the use of a single element, to expand the range of temperature for a thermistor or voltage for a varistor for a specified resistance range without any resulting loss in sensitivity.

Accordingly, an object of the present invention is to provide an improved multi-contact non-linear semi-conductor resistor which eliminates many of the. limitations of prior art non-linear semi-conducting resistors.

Another object of the present invention is, to increase the flexibility and adaptability of non-linear resistors to a Wide variety of electrical circuits. 7

Another object of. the present invention is to make possible a variable non-linear resistor by connecting the plurality of contacts to a dial switch.

Still, another object of the present invention is. to pro.- vide a multi-contact non-linear resistor which may be used in modulating circuits, either for direct current modulation or for any of the frequencies generally used by communication systems.

The invention. involves the usev of a resistor having a body of a material with non-linear electrical characteristics. A plurality of, electrically conducting or suitable metallic films or a plurality of electrical conductors are sintered into the body and a plurality of leads or corrductors are. secured in conducting relationship to the films. The non-linear resistors may include the type whose resistance varies with the applied voltage or with the temperature of the resistor. In addition, connection between the various leads may be made by means of switch controls or some movable contact arm device.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken. in connection with the accompanying drawings.

Figure 1' is a side view of a non-linear resistor having a body of rod-like shape. I

Figure 2 is a schematic diagram of a, control circuit using a resistor similar to that shown in. Figure 1,.

Figure 3 is a plan view of a non-linear resistor having a head of resistor material with five conductors pencitrating the body of the bead.

Figure 4 shows a plan view of a washer of resistor material having four metallized films deposited. on one side of the Washer.

Figure 5 is a plan view'of a washer similar'to that Patented May 3,

. 3 shown in Figure 4 but having a greater number of films, each with a different shape.

Figure 6 is a plan view of a non-linear resistor having a disk-like body and four metallized strips deposited thereon.

Figure 7 is a bottom view of a non-linear resistor which may contain contacts on the other side thereof as shown in Figures 4, and 6.

Figure 8 is a bottom view of a washer resistor simi112:1 to Figure 7 but showing the annular metallized fi s.

Figure 9 is a schematic diagram of connections show- I "acawia both sides.

ing a disk type non-linear resistor used in a modulating circuit.

Figure 10 is a plan view of a washer shaped variable resistor employing a movable contact arm.

Figure 11 is a view in side elevation of the resistor shown in Figure 10.

Figure 12 is a top plan view of another form of variable resistors employing a movable contact arm.

Referring to Figure 1, one form of the resistor includes a cylindrical rod-like body 10 of resistor material which may exhibit non-linear characteristics varying with temperature or applied voltage. A plurality of spaced conducting films 11 is deposited on the rod 10 as indicated, the deposited areas generally forming a complete ringaround the rod. Each film is connected to a conductor 12 by soldering, welding, or other suitable connecting means. Since the resistivity of the material forming the rod is much higher than the metallized films, the resistance between conductors is proportional to 'the distance between adjacent films. This resistor may be used in 'a number of different circuits applications such as a variable resistor component when connected to suitable switching means or as a control component when connected as a coupling means between two circuits.

The circuit shown in Figure 2 includes a non-linear resistor body 10 having contact rings 11, two of which are connectedto a control circuit 13 which may be a variable voltage, direct current source or it may comprise a system of communication which employs modulated frequencies of any type. A controlled circuit 14 is connected to two contact rings 11 which are spaced between the contact rings connected to control circuit 13. When the control circuit 13 changes its voltage, the resistance of the entire resistor unit 10 is changed and the resistance between the two intermediate conducting rings are changed in proportion. This change in resistg and 27 are deposited on the lower disk surface.

1 amplitude, frequency, or phase.

. resistor material having conducting strips 23 deposited on one surface of the disk. This form of resistor is adaptable for use in any circuit which will accommodate the resistor shown in Figure 1.

The resistors shown in Figures 4, 5 and 6, may have conducting films as indicated, deposited on a single side of the disk or each disk may have similar coatings on It has been found that a wide variety of circuit applications are possible when a plurality of conducting areas 21 are deposited on one side of a disk and a single annular area 24 (see Figure 7), is deposited on the other side of the disk, terminated by conductor 25. It will be obvious that the resistance paths between areas 21 and area 24 produce a wide variety of coupling combinations.

Figure 8 shows an alternate form of bottom conducting arrangement wherein two annular conductive films 26 Each annular area is connected to its conductor 28 to give additional combinations of resistance values.

The circuit shown in Figure 9 shows an additional application of a resistor disk 17 having four conductive areas 20. A source of modulating frequency power 30 is applied to opposite areas 20 on the disk thereby producing a variable resistance between the other two opposite areas. These latter two areas are connected to a source of carrier frequency power 31 to modulate its The carrier frequency power is delivered to output terminals 32 for application to a transmission circuit.

Referring to Figures 10 and 11, there is shown a resistor made in accordance with the present convention which is formed in the shape of a ring. The ring 33 is ance'may be applied to any type of controlled circuit five conducting leads 16 in the body thereof. This type of non-linear resistor may be used in the circuit shown in Figure 2; it may be used as a variable temperature responsive unit or as a temperature responsive element with a plurality of conductive leads running to a number of indicating instruments or to other linear resistors. The incorporation of the plurality of leads within the head 15 lends heat dissipating properties to the bead permitting the application of higher voltages (or power) to the bead without appreciably self-heating it.

It is often convenient to fabricate non-linear resistors in disk form since this shape is more easily adaptable to the deposition of conducting films. The disks 17 shown in Figures 4 andS can be formed with a central hole 18 for convenient mounting. The widely separated conducting areas 20 shown in Figure 4 or closely spaced areas 21 shown in Figure 5 are used as resistor terminals. This form of resistor is employed in a manner similar to that shown in Figure 2 or it may be used as a variable resistor with some suitable form of switching arrangement. 1 The resistor shown in Figure 6 comprises a disk 22 of slit as indicated at 34 to provide an air gap. Conductive films 11, similar to those shown and described in connection with Figure 1, are placed around the resistor 33. The conductive films 11 are spaced from one another in any suitable manner and at any desired interval. A contacting arm 35 is pivotally mounted upon a dielectric disk 36 located in the center of the ring 33. A lead 37 is connected to one of the conductive films 11 and a second lead may be connected to the arm 35. By swinging the arm 35 from conductive film to conductive film, a wide variety of resistance values may be selectively achieved. The properties of this embodiment of this invention are similar to that shown in Figure 1, except that the ring shape permits the use of a wiping arm type of switching arrangement.

Where a multi-contact non-linear resistor is made in the form of an elongated bar as shown in Figure 1, or a ring as shown in Figures 10, 11, the presence of the intermediate conductive bands 11, control the efiective length of the thermistor or varistor. It has been found that in such structures the width of the band must be subtracted from the actual length between the bands which are-being used to give the effective resistor length. In calibrating and manufacturing articles in accordance with the present invention, therefore, it is necessary to take into consideration the efiect of the intermediate bands of conductive material.

Referring to Figure 12 there is shown a disk type resistor 38 which is provided with an air gap 39 and a plurality of. segments 40 on one face thereof. The conductive segments 40 are selectively engageable by the contact arm 35 which is centrally disposed within a dielectric disk 38. The lower side of the disk 38 may be provided with a conductive layer (not shown) similar to that illustrated at 24 in Figure 7. A lead 25 may be as variable resistors to increase the usefulness of electric circuits.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A non-linear resistor comprising, a disk of material having non-linear electrical characteristics, a plurality of discrete conducting films arranged adjacent to the periphery of the disk, and spaced from. each other, an annular conductive film deposited on the opposite flat surface of the disk, and a plurality of conductors secured in conducting relationshipto said films.

2. A non-linear resistor comprising, a disk of material having non-inear electrical characteristics, an air gap in said disk from the center thereof to the periphery of the disk, a plurality of discrete conducting strips deposited on one surface of said disk, said strips comprising,"

metallic areas having parallel, straight, spaced borders, a conductive film deposited on the opposite flat surface of the disk, and a conductor secured in conducting relationship to each of said strips.

References Cited in the file of this patent UNITED STATES PATENTS 1,992,410 Benkelrnan Feb. 26, 1935 2,005,922 Stoekle June 25, 1935 2,119,195 Bagno May 31, 1938 2,134,870 Fruth Nov. 1, 1938 2,744,986 Caldwell May 8, 1956 FOREIGN PATENTS 560,769 France Oct. 10, 1923 533,214 Great Britain Feb. 10, 1941

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