US2063826A - Resistor - Google Patents

Description

H. PENDER Dec. 8, 1936.

RESISTOR Filed June 1, 1932 INVENTOR flarolal Fender ATTORNEYS Patented Dec. 8, 1936 UNITED STATES PATENT OFFICE national tance Company, Philadelphia,

Pa.,a corporation of Delaware Application June 1, 1932, Serial No. 614,679

5 Claim.

This invention relates to the construction of electrical resistance devices and, with regard to certain of its more specific features, to resistors for radio apparatus.

One object of the invention is to provide a resistor for radio use having a high power rating. Another object of the invention is to provide a construction for electrical resistance devices which is impervious to moisture. Another object of the invention is to provide a thoroughly insulated resistor. tion is to provide a resistor having excellent heat dissipating qualities. Another object of the invention is to provide a device of the above nature which is simple in construction, durable and inexpensive to manufacture.

Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly consists in the features offconstruction, combinations of elements, and arrangements of parts as will be exemplifled in the structure to be hereinafter defined and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which are shown three of the various possible embodiments of the mechanical features of this invention,

Figure 1 is a side elevation of a resistance device constructed in accordance with the invention;

Figure 2 is a sectional view taken on the line 2-4 of Figure 1;

Figure 3 is a perspective view of a plug;

Figure 4 is a longitudinal sectional view similar to Figure 2 showing a modified form of resistance device;

' Figure 5 is a longitudinal sectional view showing a further modification; and

Figure 6 is a cross-sectional view taken on the .or tube II preferably constitutes an insulator for .high frequency and for high voltage charges and nevertheless is preferably composed of a mate rial having relatively high heat conductivity. Preferably also it is impervious to air and particularly to moisture in any form, and preferably it is strong and durable. Although there are several substances fulfilling one or more of the above requirements which I might use, I prefer Another object of the invento employ for the insulator ID a ceramic such as unglazed porcelain or a substance of the nature of porcelain. The rod IIl may be generally cylindrical, or it may be prismatic, or it may have such intimate contact with the wall thereof as to leave substantially no air space surrounding it, is the resistance element I2. Preferably this resistance element I2 constitutes a glass rod or fiber coated with carbonaceous substance, such 'as the resistance element disclosed in my prior U. S. Letters Patent #1,832,419 granted November 17, 1931. Such a resistance element is to a high degree flexible, and has a coating of resistance material hard and firm enough to withstand the operation of forcing the rod into the capillary passage II without scrapingofl. or injuring in any way the coating. Preferably the capillary passage I l' is circular in cross-section because the resistance material I2 may be more readily and accurately made of a cylindrical rod or fiber.

Referring to Figures 1 and 2, in a side wall of the rod or tube and near the ends thereof 1 form a pair of bores I3, I3. These bores intersect the capillary passage I I and the resistance element I2 extends into and preferably through each of these bores I3, I3.

Referring now to Figure 3, I provide a plurality of metal plugs ll adapted to m m the bores n,

I3. Each plug is generally cylindrical in form and has formed therein a slot II at one end of a. size to straddle the resistance element It.

Preferablythe plugs are made of metal alloy of such a nature that,upon solidification from a molten state, it will expand to such an extent as to press firmly against the walls of the bores I3 and be compressed against the resistance element I2 without, however, fracturing the insulating -rod or tube I8 or \the resistance element II, as-

suming the resistance element to comprise a coated glass rod or filament as described.

Preferably, also the alloy should be of such a nature that it will melt at a temperature low enough to facilitate the manufacture of the articles in quantity production without danger, however, of fusing in operation. The alloy also should have good flowing properties so as to conform to the minute irregularities of the ceramic or the like. The ingredients of an alloy having the above mentioned qualities in a marked degree, which is an example merely of a. preferred alloy, are as follows:-

- Per cent Antimony 9 to 15 Tin -Q 4 to 6 Lead 87 to 79 Other advantages of the above and similar alloys are that they will not burn the resistance coating of the resistance material I2, and they have a low coefiicient of expansion while in a solid state, comparatively close to that of glass.

I now place a plug I4 in each of the bores I3 so as to locate the resistance element I2 in the slots I5. I now heat the entire article to a sufficient temperature to melt the plugs I4, and the metal then flows around the resistance element I2 and fills the bores I3, I3. The advantages of proceeding in this manner are that the metal is able to reach all parts of the bore readily, and as the ceramic is at the same temperature or an even higher temperature than the metal there is no sudden cooling on contact such as results from attempting to pour molten metal. I have found that for the filling of small bores this method of molding metal secures a more perfect casting.

While the metal is molten, I introduce into the bores I3, I3 terminal wires IE, IS. Such terminal wires are bendable and may desirably be of copper coated with tin which, having little resiliency, will assume any desired shape. Such wires are excellent conductors of electricity and have a strong affinity for alloys of the character indicated. Desirably the ends of the wires I6 that are introduced into the bores I3 are knurled or crimped as shown at I! so that a firm union between the wires and the solidified metal may resuit.

In the manufacture of resistors as above described I have found it advantageous to clamp or otherwise secure the bodies I0 upon a conveyor leading into or over a furnace, and an operator may insert the terminal wires I6 when the plugs I4 have melted; the conveyor then carries the re-' sistors beyond the heating locus and the metal quickly solidifies, whereupon the resistors may be removed or may automatically be deposited in a box or the like.

The metal alloy, upon solidifying, expands against the walls of the bores I3, I3 and becomes firmly attached to the rod or tube I0 and is compressed against the resistance element I2. The

electrical connection between the resistance ele,

ment I2 and the terminals I6, I6 is found to be substantially noiseless in an audio circuit.

After the alloy has solidified in the bores I 3, I3 (and either before or after the resistors have been taken from the conveyor) moisture-proof insulating material is introduced upon the top of the metal filling the remainder of the bores, as the amount of metal used is preferably less than enough to fill the bores I3, I3. As examples of such moisture-proof insulating material I have obtained good results by using rosin, or Canada balsam. Such substance forms insulating portions I8, I8, and desirably also is introduced into the ends of the capillary passage II forming insulating portions I 9, I 9. When either rosin or Canada balsam is used, it is found that the insulating material penetrates by capillary attraction or like force into the minute spaces between the now solidified metal portions I4, I4 and the wall and bottom of the bores I3, and effectually prevents moisture from reaching the resistance element I2 and also acts as a cement to further increase the adherence of the metal I4, I4 to the ceramic I0.

Referring now to Figure 4, a modification of the invention is shown in which molded metal portions 20, 20 are introduced into recesses 2|, 2| formed in opposite ends of the insulator Ina. These molded metal portions 20, 20 may be and preferably are of the alloy above indicated or having similarcharacteristics, As the recesses 2|, 2| are somewhat larger than the bores I3, I3 I may introduce the metal into the recesses in liquid form, although the method of using a plug and melting it in position may also be adopted. Extending into each recess 2I is a lateral bore 22 through the cylindrical wall of the ceramic Inc, and through which lateral bore extends a terminal I 5a the inner end of which, embedded in molded metal 20, may be of question-mark shape as shown in Figure 6 to make a firm union between the terminal and the molded metal 2!]. Covering the ends of the metal 20 are layers of moistureproof insulating material 23, 23, desirably Canada balsam or rosin, which acts to firmly cement the met-a1 20 to the ceramic Illa and keeps moisture from the resistance element I2 as already described. Desirably a drop of this insulating material is placed on the outside of the lateral bores 22 sealing any space between them and the wires I 5a, I 5a.

Referring now to Figure 5, a further modification is shown in which terminal wires I5b, preferably of the shape shown in Figure 5, are introduced directly into recesses 24 so as to project from opposite ends of the unit. The recesses 24, 24 may be undercut as indicated and any of the methods of introducing the molded metal 25, 25 already described, or any other suitable method, may be adopted. Preferably the unit shown in Figure 5 is also sealed against entrance of moisture by means of moisture-proof insulating coatings 26. By reason of the undercut portions of the recesses 24, and by reason of the shape of the terminals I5b, this unit has great strength.

The resistance devices herein described are thoroughly insulated both on sides and ends so that several resistors may be placed in close contact with each other in the apparatus in which they are used. Furthermore, they are small, light and extremely durable. I'he resistance coating of the resistance element I2 is in intimate contact with the substance of the insulator thus dissipating heat materially increasing the power capacity of the device. Porcelain and similar substances are good conductors of heat and give the resistors a high power rating. By uniting the terminals I5 to the resistance element with molded or cast metal within the insulator ID a device having a ,small maximum diameter is obtained and thus space, which is at a premium in a radio set, is conserved. Furthermore, except for the terminals I5, there are no exposed conductive parts, and after soldering the terminals to whatever they are to be connected to in the radio apparatus, the surplus length thereof may be cut off with a pair of pliers. The resistors of the present invention are particularly adapted for mounting in gang formation.

It will thus be seen that there has been provided by this invention an article in which the various objects hereinabove set forth, together with many thoroughly practical advantages, are successfully achieved. 1

As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illust'rative and not in a limiting sense.

In the following claims the term molded" is to be construed as meaning cast, liquefied in position, formed by dropping liquid upon something, orspraying with atomized substance, as the term does not in reality relate to any particular process (as used herein) but is indicative of a particular condition of metal or other substance, for from the standpoint of audio-frequency apparatus a connection made in one of the above indicated manners or in any similarmanner is, in the sense of an article of manufacture, difierent from a mere mechanical union, in intimacy of contact and molecular condition of the parts, and so likewise is a seal or covering for insulating or keeping out moisture.

I claim:

1. In a device of the class described, a glass rod filamentary in diameter, a coating of carbonaceous resistance material on the cylindrical surface of said rod but not on the ends thereof, a right cylinder of insulating material enclosing said rod and said carbonaceous substance, the cylinder being slightly longer than the rod and the rod and the cylinder being coaxial there being a passage in the cylinder just large enough to conveniently hold the rod, bendable metal wires extending axially from opposite ends of the cylinder said wires constituting the only break in the insulation of said device, and additional more readily conductive material directly contacting the ends of the rod and the carbonaceous substance thereon and also contacting the wires and holding them in place.

2. In a-device of the class described, in combination, a tubular member formed from insulating material, said tubular member having recesses in its opposite ends, the dimensions or said recesses being greater at points spaced irom the ends of said tubular member, a resistor rod disposed within the bore of said member and having its end portions disposed within said recesses, metal in said recesses surrounding and embracing said end portions of said resistor rod and engaging the walls 0! said recesses at said points, and wire terminals embedded in the metal or each 01' said recesses.

3. In a device of the class described, in combination, a tubular member formed from insulating material, said tubular member having recesses in its opposite ends, the dimensions of said recesses being greater at points spaced from the ends of said tubular member, a resistor rod disposed within the bore 0! said member and having its end portions disposed within said recesses, metal in said recesses surrounding and embracing said end portions of said resistor rod and engaging the walls of said recesses at said points, wire terminals embedded in the metal of each of said recesses, and an insulating substance sealing the end portions of said recesses.

4. In a device of the class described, in combination, a tubular member formed from insulating material, said tubular member having recesses in its opposite ends, the dimensions of said recesses being greater at points spaced from the ends of said tubular member, a resistor rod disposed within the bore of said member and having its end portions disposed within said recesses, metal in said recesses surrounding and embracing said end portions of said resistor rod and engaging the walls of said recesses at said points, and wire terminals having bent portions embedded in said metal.

5. In a device of the class described, in combination, a tubular member formed from insulating material having recesses formed in its opposite ends, the diameter of the inner portions of said recesses being greater than the diameter of said recesses at the ends thereof, a glass rod having a. carbonaceous substance coated thereon fitting within and substantially filling the bore of said tubular member and having end portions extending into said recesses, metal filling the portions of said recesses having enlarged diameters and embracing said end portions of said rod, and wire terminals embedded in said metal and extending outwardly therefrom substantially in axial directions with respect to said tubular member.

HAROLD FENDER.

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