US2866879A - Coaxial resistor - Google Patents

Description

Dec. 30, 1958 J. J. CERNY COAXIAL RESISTOR Filed Sept. 3, 1957 COAXIAL RESISTOR Joseph J. Cemy, Chicago, Ill.

Application September 3, 1957, Serial No. 681560 4 Claims. (Cl. 201-63) The instant invention relates to electrical resistance devices and the like. More particularly, it relates to a construction adapted for what is referred to in the trade as a coaxial resistor.

A conventional coaxial resistor is a resistor or electrical resistance construction which ordinarily comprises a bored core of some suitable dielectric material such as ceramic or the like. The core is usually of cylindrcal configuration and has a resistance wire wound on and about the outer curved surface. A pair of terminal wires extend outwardly from the bore of the core in opposite directions and axal alignment. Each terminal wire is connected to an opposite end portion of the resistance wire. Conventionally a fused enamel or other suitable dielectric coat covers the resistance wire and the core upon and about which the resistance wire is wound.

Various mechanical expedients have been conventionally 'employed to secure the resistance wire to the terminal wires to provide rgid securance of the inner end portions of the .resistance wire within the core and to securely fasten the resistance wire to the opposed terminal wires.

While the prior devices of the class described provide good resistors, their utility is frequently short-lived because they are ,unable to withstand extremes of physical handling, by reason of the fact that the mechanism employed 'to connect the resistance wire to the end terminal wires changes the general geometric contour of such prior resistors. This variation in contour results in weakening, thinness or unevenness in the enamel coating conventonally covering the prior resistors, resulting in a predisposition or tendency for undesired grounding of the resistors.

Most suitably, the means for connecting the end termina wires to the resistance wire of a coaxial resistor should be some contrivance which does not appreciably extend from or change the general cylindrcal contour of the core. Thereby, when the enamel coat is fused about the core and the resistance wire mounted thereupon, the enamel coat will be fused without causing undesirable exposure of the resistance wire resulting from the adhesive characteristics of the enamels conventionally used in connection with coating resistors.

In accordance with the instant invention and as an object thereof, there is provided an electrical resistance construction or resistor in the class described having means for connecting the resistance wire with the end terminal wires and being wholly within the general geometric contour of the core of the resistor.

It is a further object of the invention to provide an electrical resistance contruction or resistor comprising a core about which an electrical resistance wire is wound and a pair of axially disposed terminal wires anchored within the core and extending outwardly therefrom and means anchored within the cores secured to and elect t s. P nt ICC apparent from the following description and appended claims, reference being had to the accompanying drawings and numerals of reference thereon.

On the drawings:

Fig. 1 is an exploded view showing the relationship of the resistor core, the terminal wires and the connectors, the core being shown in longtudinal section.

Fig. 2 is a longitudina] sectional view of a completed resistor illustrating one embodiment of the instant invention.

Referring now more particularly to the drawings, a core or base 10 is provided which is of general cylindrical configuration. The core 10 is of some suitable dielectric fabrication such as a ceramic material, the

t coeflicient of expansion of which can be optionally varied in accordance with requirement by varyng the compo sition of the materials comprsing the fabrication.

The core 10 has provision for disposition therein of the inner end portions 11, 11 of a pair of axially disposed oppositely extending terminal wires 12, 12. Such provision in the embodiment shown is by means of an axially disposed bore 13 extending longitudinally through the core 10. The bore 13 is preferably of a diameter substantially the same or slghtly larger than the diameter of the terminal wires 12, 12 so that the terminal wires may be readily manually inserted into the position illustrated in Fg. 2 without permitting any substantial degree of play of the portion of the terminal. wthin the core. Such arrangement provides for 'coaxal disposition of the terminal wires.

In each of its opposite end portions, the core 10, in the embodiment illustrated, is provided with a diametric bore 14 which intersects the axal bore 13 so that a pair of branch or radial bores extend outwardly and perpendicularly from each end portions of the axal bore 13, as clearly illustrated in Fig. l. A metal plug or electrical connecter 15 is positioned in each radial branch of the diametric bores 14.

In assembly of the resistor, the terminal wires 12, 12 are first inserted within the axal bore 13. Thereafter the electrical connectors 15, such as metal plugs, are inserted in their respective radial bores. The connectors 15 are Originally of a diameter substantially equivalent to or slghtly smaller than that of its respective bore 14, and they are of a length slghtly longer than or substantially equal to the radius of the core 10. That s to say, the connectors 15 when disposed in assembled position as illustrated in Fig. 2 will rest upon their respective terminal wires and, at their outer ends, extend just slghtly beyond the surface of core 10.

After arranging the foregoing parts, a resistance wire 16 is wound about the core having certain portions or convolutions thereof in engagement with the outer end of each Connector 15. Thereafter, with a welding device (not shown), a number of strands of the resistance wire 16 are welded to each connector 15 and each pair of connectors is simultaneously rigidly secured by welding to its respective terminal wire 12, as illustrated in Fig. 2. Because of the application of slight pressure during welding, the excess in length of each connecter 15 is &865379 forced back into its respective branch of bore l4. Such pressure insures cngagement and subsequent welding of the inner ends of each Connector with its respective terminal wire 12 and anchoring of the rconnector within its respective bore, which it is adapted to fully fill. I

. After assembly of the electrical components of the resistor, a dielectric coat 17, such as an enamel frit s applied on and about the resistance wire 16' and .the ends of core 10 and subsequently fused. By proper selection of the materials and their proportions, the coeicient of expanson of the enamel coat 17 can be selectively varied. p

Because of the confinement of the Components of .the assembly as closely as possible to the general cylindrical configuration, crazing or cracking of and exposure of wire 16 because of the cohesive characteristics of the enamel coat 17 will be held to a minimum. The most likely place of weakness in the instant Construction will be at the ends of the core adjacent to the terminal wires 12, 12. Crazing or cracking of the enamel at these positions 18 will not afiect the life of the resistor as the resistance wire cannot be exposed at these positions.

As many changes or substitutions could be made in the above described Construction and as many apparently widely difierent embodiments of the nvention within the scope of the claims could be constructed without departing from the scope and spirit thereof, it is intended that an matter contained in the accompanying specification shall be interpreted as being illustrative and not in a lmiting sense.

I claim:

1. An electrical resistance element comprising a passaged non-conductive core; a resistance wire wound about said core; a pair of disconnected electrical terminals extending outwardly from said core, said core having a plurality of Connector-containing bores a''anged` in opposed radal pairs, each of said bores opening on the outer surface of and the passage in said core; an electrical connector in each connecter-containing bore being of a length substantially equal to the length of its respective bore, said connectors completely occupying their respective bores and securing the terminals within said core and being Secured at their inner ends to said terminals and at their outer ends to said resistance wire.

2. An electrical resistance element comprising a nonconductive core; a resistance wire wound about said core, said core having a longitudinally disposed bore therein; a pair of opposed non-connected electrical end terminals disposed within said lonigtudinally disposed bore; two pair of Connector-containing bores in said core arranged in pairs perpendicular to said longitudinal bore, each pair of said Connector-containing bores in association with one of said end terminals, respectively; electrical connectors in said Connector-containing bores welded at their inner ends to said terminals and welded at their outer ends to'said resistancewire.

3. An electrical resistance element compr'sng a nonconductive core; a resistance wire on the outer surface of said core; a pair of disconnected electrical terminal wires extending outwardly from within said core, said core having a pair of connecter-containing bores associated with each terminal wire; an electrical connecter in each Connector-containing bore being of a length substantially equal to the length of its respective bore, said connectors Secured at their inner ends to said terminal wires and at their outer ends to said resistance wire.

4. In an electrical resistance element of substantially single resistance, the combination of an axially passaged non-conductive core, a resistance wre mounted about said core on the outer surface thereof; and a plurality of terminal wires extending co-axially from said core, with a pair of electrical 'connectors Secured at their inner ends to each of the terminal wires the connectors of each pair being disposed on a common diameter, the outer and inner ends of said connectors being substantially flush with the outer and inner surfaces of said core, said connectors, at their outer ends, Secured in electrical connection to said resistance wire.

References Cited in the file of this patent UNITED STATES PATENT S 1,432,435 Abbott Oct.. 17, 1922 2,008,288 Malone July 16, 1935 2,063,826 Pender Dec. 8,` 1936 2,773,159 Taggart --M-.-a Dec. 4, 1956

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