US1582141A - Electrical resistance material - Google Patents

Description

, tivity.

Patented Apr. 27,- 1926-.

"PATENT OFFICE.

JOHN S. NOWOTNY, OF CINCINNATI, OHIO.

ELECTRICAL RESISTANCE MATERIAL.

K0 Drawing.

To all whom it may concern Be it known that I, JOHN S; NQWOTNY, a citizen of the United States, and residing at Cincinnathin the county of Hamilton and State of Ohio, have invented a new and useful Improvement in Electrical Resistance Material, of which the following specification is a full disclosure;

This invention relates to the discovery of certain new and unique electrical property materials and to the process of making. The principal object of the invention or d s covery is to produce a composite vmaterial having a predetermined and definite electrical property, such as resistance or conduc- Another object of the invention is to produce such a material of a nature. adapting it to fabrication by molding or pressin or otherwise working into the shapes desired, adapting the material to be constituted into any suitable electrical apparatus element.

That is to say, a property of this material is that it can be fabricated either un-- der cold or heat processes, as a dry, plastic or molten mass, depending upon the particular electrical apparatus element required.

In consequence, the element so formed from my new material may be given any desired mechanical strength, size of element, cubic or areardimension, having a predesired thermal electric current conductivity or resistivity and which will also be a durable and staple article, the predesired electrical property being constant and not sub ject to the usual variations such as increasing resistance under repeated beatings.

I have discovered that various materials or substancesof relatively varying electrical property, each of which is capable of reduction by crushing, grinding or attrition into agranular or (powdered mass, can be mixed or combine into a substantially homogeneous solid body, which body also is characterized by being relatively nonducti'le, capable of being reduced by attri-, tion.

The required electrical property can be definitely predetermined and controlled and rendered constant by the selection of and the relative proportions sot .the series of components, each of which has a different coelhcient ot' the desired electrical property as lnstanced by reslstance.

Application filed um 13, 1921. serial No. 477,265.

Example, to construct a resistance element of high percentage, resistance-materialsof low conductivity are employed, and for an element of "low percentage resistance, ma-

terials of high conductivity are used.

It is a. characteristic of my newly dis-' covered inaterialthat a given compound,

, that is, a given selection of material of different electrical properties combined'in a given proportion through a wet process whereby a plastic mass is molded into shape and dried, possesses a different degree of resistivity, than the same kind and proportion of materials when fabricated by ceramic processes. A

The discovery is clearly distinguishable electrical property, which coeificient remains constant.

Metallic resistance material is usually of low resistivity, while if refractory metal orcompounds are used, which may have a hi 11 specific resistance to be used on high vo tages, such materials are generally fragile and cannot be molten under commercially variable temperatures so as to be molded or cast into the desired shapes. Such ma-. terials, having vitreous properties, are undesirable heater elements' and materials which I have discovered and constituted are relatively nomvitreous.

As illustrating fields of usage for my material they are generally adapted to consti- 9o tute any desired electrical apparatus element such as heating devices, rheostats for controlling currents or fields of electrical enerators, starting boxes for raduating the 0 how of electric current throug motor arman5 a granular or powdered state and blended and combined in proportions determined by the desired electrical property.

hen it is desired to produce an electrical resistance material of high percentage, the product -is composed of certain proportions of these materials of low conductivity. For

medium or low resistance; a lesser amount or proportion of the low conductive materials and a greater amount or proportion of relatively high conductivity materials are If the press is employed with a gauge device.

indicating the pressure in pounds applied,

and the press 1 dies or molds equipped or in connection with electrical measuring instrument, as an olmi-meter, the mass can be pressed into as compact. a body as may be desired and the ohmic resistance accurately determined while the body is being formed.

Under a ceramic treatment or process the blended or-conglomerate electrical resistance material may becombined with a bonding material, preferably of neutral characterin a dry, semi-dry or liquid form and conditioned to make it workable for forming into the desired shapes under hydraulic or mechanical press pressures. The shaping of the resistance bodies can also be earned out by any of the well-known methods of uniting plastic materials. For curing, the bodies are then dried and placed in a suitable kiln or electric furnace. The temperature of the kiln may be raised sufliciently to thoroughly bond the materials or raised up to'or beyond a firing point in order to eliminate or expel any foreign matter that may afterward be detrimental to the use of the composite under extraordinary temperatures, such as electric heating devices, or any beyond those employing ordinary temperatures, such as motor starters and controls and generator field controls. The heating or firing temperatures regulate the internal resistance of the body and a variation is produced by high or low temperatures.

The composite, as a body, may be heated by passing an electric current of suiiicient amperage therethrough, so as to cause an in tense heating of the composite and thereby bring the molecular parts, having an affinity for each other, into close or intimate contact with each other by thermo-union or electric welding. That is, the constituted material is preferably cured and so rendered staple and constant asto electrical property.

After such electric treatment, the body memes may be again reduced by crushing and grinding, and the crushed material utilized as an article of commerce, for making resistance bodies, either by pressing, plastic evident that the range of materials available.

is quite extensive, and in giving examples, it is the purpose of stating them by way of illustration, and not as limiting the scope of the invention.

Also, it is my objectto give examples with which I have obtained best results, and also to give due consideration to the cheapnesls and commercial availability of materia s.

In general, the materials may be understood as embracing a combination of relative-1y high, medium, and low resistance material, lending itself to the arbitrary formula H ML. As an example of high resistance component, I have obtained the best results from the use of hydraulic cement, or any like material which will harden in water. oxide of calcium mixed with fire-clay, or the like, constituting the H formula element. As an example of the medium resistance component, best results have been obtained from the use of iron or tungsten oxide, or the like, which will be the M component of the formula. For the low resistance element, I preferably employ graphite, or coke,

thus deriving the formula H M L. These materials are each reduced to a fine powder, and thoroughly mixed and blended for treatment in an electric furnace, preferably of the type in which the treatment charge is subjected to an electric current. As a proportional example, say I use 55% H, 40% M and 5% L, bringing it to a molten state, and adding, if desired, additionalL to compensate for the loss of carbon by oxidation.

The treated material is taken from the furnace as an ingot, and it is a unitary body, in the nature of. an alloy, having substantially homogeneous molecular electrical resistance, of say 1000 ohms per unit mass. This ingot product is suitable, say for a field control element and can be cast into the desired shape and structure; Or, the ingot material can be ground into a powder and by ceramic process pressed into a suitable electrical apparatus element structure.

But, if I desire say a heating element, the ingot body having too great a resistance, is itself taken as the H element, for an additional ceramic treatment. That is. the ingot is reduced to an H powder and again molded or blended with the M and L elements.

To indicate the lesser resistance property of the ingot material in relation to the original high resistance material, it may be desducing a heating element.

that Say I desire a heating element of approximately 5 ohms resistance per unit mass, I powder, mix and blendsay 60% H- 30% M and 10% L, preferably in a wet state, using water, silicate of soda, molasses, coal tar, orthe like as a bonding agency. This plastic mass is placed in a suitable (hydraulic) press and pressed into a shape or size corresponding to the structural nature of the desired element. The specific gravityfas well as the ohm resistance, per unit mass, will depend somewhat upon the degree of pressure, which is,'of course,'controllable, and I recommend say a pressure'of 2000' pounds to the square inch.

The element so formed is a brick-like body, having a uniform and substantially constant resistance, itis non=ductile, reducible by attrition, substantially non-vitreous and physically entirely suitable to its usage, as well as having the predesired electrical properties. Moreover, it may be given any desired specific gravity, area Or cubic dimensions, as well as structure desired;

It will, therefore, be readily understood, and the importance of the fact observed,

that by the selection and proportion, of the- H M L elements. in the first instance, or the H- M L elements in the second instance, and the )ressure being a controllable agency,

l can, within a practical degree controllably predetermlne not only the coeflicient of ohm resistance per unit mass, but the specific gravity, size, shape, structure and cubic or area dimensi0ni. e. shape and area of radiating surface of the heating element depending upon its condition of usage or the apparatus requirement. a

As another example, if the proportions for the ceramic treatment be, say H- 3070 M and 20,.)L, the product would be substantially 3 ohm resistance per unit mass with a given ressure.

give a product, say, having a 2 ohm resistance per unit mass with the given degree of pressure.

In constituting the primary or ingot material, say it be known or determined that the ohm resistance of the H is 10000, of the M 1000, and of the L. 5, the ohm resistance of the resultant product will depend upon the proportions, and this has to be determined and tabulated.

The same is true of the ceramic formula H- M L. Without attempting the infinite proportional elaboration examples selected will su co to furnish a key enabling the discovery to be operated and in terms of formula, with a reasonable degree of accuracy and obtaining any de" sired coeliicient of resistivity or conductiv- 50% M- and 20% L, would.

ossible, the fewity. That is to say if the given 3 different proportions of the M L bodies be made,

their ohm. resistance per unit mass, and with a given pressure,'and their specific gravity determined, the results can be tabulated, as.

for example 00% H-3 2, M, 10% L:

' 5 ohm per unit mass. 50% H-30% M, 20% L: i

5 ohm per unit mass. 30% H50% M, 20% 1L:

2 ohm per unit mass.

The proportions can be infinitely varied, and a working table so compiled from the determined data, enabling a most elastic and selective range of values to be obtained suitable to the requirements of a given usage or an arbitrary requirement if desired for any particular purpose.

It will thus be seen that the exact substance and proportions are not of limiting import inasmuch as this, disclosure constitutes an entirely practicable, controllable and workable basis for obtaining the desired materials 01:.products.

Series AIf it be desired to produce a material, say'about 1000 ohm resistance per cubic centimeter, which. may be relatively regarded as ahigh resistance 1nateriai .A-FormulaH. 50% M. 40% L. 10%

material say ohms to a cubic centimeter Takea formula H. 10% i M. 4O% L- 0% Before or after having been pressed into shape and thoroughly dried, place in enclosed sager or retort and heat for about 48 hours, at a temperature of near 750 F. 400 C. Series D-If still lower resistance is desired, say 50 ohms per cubic centimeter, after C mass or unit has'been allowed to cool, rebake formula C mass or unit for about 48 hours at a temperature of near 1500 F.- 820 C. This will reduce C to D.

Series E-The resistance may again be lowered say to one ohm per cubic centimeter lid will decrease the ohms resistance,i,or a greatcr proportion of Hor M-'- will proportionally increase-the resistance.

Or increased pressure in forming intoshape will decrease the resistance-:or an increased temperature short of the destructive point in the baking or heating will more thorou hly flux and consequently'ibring the molecu ar parts into closer contact, hence will decrease the resistance of the alloy so formed. It may be fully understood that anyone skilled in the art and beingprovided with the various formulas and a key to them, can readily. produce commercially in any quantity, a resistance material th 1: will fully meet all the requirements of the rade, from the lowest say .50 ohms to 50,000 or more or less ohms per cubic centimeter, as may be required and predetermined by ai d at the will of the o erator manufacturing \various formulas T e materials used toniake H. -M. L. formulas may be blended in their "proper proportions and then heated to .n ever temperature needed .to st the. desired resistance of the mass or ingot without having been shaped. This mass of material can then be'taken from furnace, retort or sager in bulk, as H. formula numbered, M. formula numbered and L. formula numbered,

for the use of manufacturers of resistanceappliances, and can be formed into any desired shape or predetermined resistance .to suit the requirements-then heated or baked to finish product for use.

It can readily be observed that by employ ing the. H. M. L. series of varying resistance material, I can easily balance my proportions and predetermine the exact resistance of unit, mass or individual element alloy in process of formation. A slight addition of H. and a small reduction of L., would cause increased resistance, or a slight addition of L. and a small reduction of H., would cause a reduction of r esistanceor more or less of M. added to H. or L. would change the resistance in either a high or low direction, the percentage in the amounts of H. M. L., would be followed automatically by an increased or decreased ohms resistance in the finished product so formed.

To produce an L. mass of very low resistgreater proportion or percentage of L in relation to M and ,H-

sirable formula which I indicate as formula F. in which I employ proportions viz H-20% by weight. M% by weight. L-20% by weight. y

been thoroughly mixed or blended, the entire mass before being moulded into shape placed in retort or furnace and heated to a temperature of about 1800 F.-'-985 C.

While being fused in retort or sager the free circulation of air is excluded, that is to say, the retort is sealed to create a semivacuum, the heat pressure in the retort preventingthe outer air from entering freely into retort, of course the gas liberated from a WVhile I have disclosed this general H. M.

'L. formula, as the best means of explaining the usage of this discovery, I do not mean to be understood as limiting the invention to a material necessarily limited to three components only. F or instance, it may be de-' sirable to embracein the H. unit, several species, such as a cement or fire-clay, or in the M. unit, say both manganese and iron oxides, but this is mere additionand not sub traction from this disclosure. So the H unit or the M. unit, may each embrace several analogous components, provided the members of the H. group or the M. group respectively,

havesufiicient approximation of fusion pointsr For'instance, I would not recommend iron and lead oxides as joint components of the M. element, because of the very different fusion points, and because lead tends to globulize when fused with other metals, while tungsten oxide is usable.

It will also be observed that substances usable and classifiable in relation to the H. and M. formulasymbols are preferably metallic oxides, usable with such a flux as borax.

The A, B, C, D and E examples I have given as illustration, may be regarded as primary masses, though each in itself is formed of H. M. L. components, that is to say, the H. M. L. material of example A, ma constitute the H unit, the H. M. L. material of example B the M. unit, and the H.

M. L. material of example E may be the L. unit, selected to constitute the ultimate H. M. L. material or finished product.

Thus the finished product may, on last analysis, comprise quite a variety of different chemical substances, or it may contain only three, but in either event, it conforms to the underlying principle of a resistance material, the specific resistance of which is due to the controllably balanced use of high, medium and low resistance materials, in selected proportions, and the resistance being also. predeterininately influenced by the treatment temperature, or by different pressures, in the instance of foramic fabrication.

In the effort to disclose a completely workable basis for utilization of the discovery in the broadest aspect, itis to be understood that I make no claim to scientific accuracy in any theories advanced.

I wish todirect attention to the fact that this present; application is intended to be. substituted for my ,pendin application, Scrial No. 370,282, filed Mare 31, 1920, which original application will be abandoned in favor of the present case, after it has receivedfiling date and serial number, so as to constitute the present case a continuation of said original.

Having described iny invention, I claim: 1. The herein described process of forming aresistance element material, consisting in, mixing in selected proportions, a very high, a medium and a very low resistance material, and then subjecting them to heat and blending them into a substantially ho-' mogeneous composition, then mixing the material with different proportions of relatively medium and low resistance materials, and uniting them by ceramic treatments.

2. The herein described process of forming an electrical apparatus element product, which consists in first forming by heat treatments 2. slag-like body containing selected materials of variable electrical resistance,

second, reducing the body by attrition, grinding or crushing, and mixing it with predetermined proportions of like materials of variable electrical properties, and third,

forming it into a unitary body.

3. The herein described process of forming an electrical apparatus heater element, consisting in forming a slag-like body of relatively high, medium and low resistance materials, constituting first, a relatively high resistance material, second, reducing the same and mixing it with materials similar to the original medium and low resistance materials, and third, forming them into a unitary body.

l. The herein described process of forming an electrical apparatus element, consisting of forming a slag-like body of materials of variable electrical resistance conforming to the general formula H. M. L. to constitute a H- material, second, reducing the slag and mixing it with variable resistance materials conforming to the eneral formula H- M. L., and third, forming said mixture into a substantially homogeneous and unitary body. v

' In witness whereof, I hereunto subscribe my name.

JOHN S. NOIVOTN Y.