US3183466A

US3183466A - Inductive electrical component

Info

Publication number: US3183466A
Application number: US283225A
Authority: US
Inventors: Joseph J Martus
Original assignee: Nytronics Inc
Current assignee: Nytronics Inc
Priority date: 1963-05-27
Filing date: 1963-05-27
Publication date: 1965-05-11
Anticipated expiration: 1982-05-11

Description

United States Patent Ofifice 3,183,466 Patented May 11, 1965 3,183,466 INDUCTIVE ELECTRICAL COMPONENT Joseph J. Marius, New Providence, N.J., assignor to Nytronics, Inc., Berkeley Heights, N.J., a corporation of New Jersey Filed May 27, 1963, Ser. No. 283,225 6 Claims. (Cl. 336-192) This inventioin relates to improvements in electrical components and more particularly to improvements in the electrical characteristics of such components.

In the manufacture of certain radio frequency inductors it is very desirable to employ leads which are made partly of ferromagnetic material, such as for example dumet leads, because of their good welding characteristics. However, the presence of such a ferrous metal within the electrical field of the inductor results in a substantial amount of electrical degradation of the coil. This degradation is measurable in terms of the Q, that is the figure of merit of the coil and its effect has been found for certain values of inductance to decrease the Q of the coil by an amount up to approximately 35%. This prob lem becomes more acute for inductors of miniature and subminiature size since in these inductors the degradation cannot be significantly reduced by relocation of the leads.

Accordingly it is an object of this invention to provide an electrical inductor in which the electrical degradation of the coil due to the effect of the leads is either entirely eliminated or at least considerably minimized.

It is another object of this invention to provide inductors of miniature or subminiature size having substantially higher values of Q than could be obtained heretofore in inductors of equivalent size which employed ferromagnetic leads.

All of the objects, features and advantages of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing, in which:

FIG. 1 shows in axial cross section one embodiment of an inductor manufactured in accordance with the principles of the invention,

FIGS. 2a and 2b show enlarged views of the type of lead employed in the construction of FIG. 1, and

FIG. 3 is a graph showing a comparison between the Q values of coils of prior art construction and those made according to this invention.

Referring now to FIG. 1, a coil is wound about a coil form or core 12 which in the drawing is cylindrical in shape, but which may be other shapes as Well. Fhe core 12 is preferably of ferrite but may also be made of iron, phenolic or other suitable material and is provided with an axial bore 14, which as shown, may extend from one end of the core to the other. Leads 16a and 16b are inserted in the bore 14 at opposite ends of the core 12. If desired the bore may be replaced with a recess at each end of the core. The ends 18a and 18b of the coil 10 are suitably connected as by soldering or welding to the leads 16a and 1612.

Referring now to FIG. 2, each lead 16a, 16b comprises a nib portion 20 and an elongated portion 22. The nib portion 20 is made of a suitable non-ferromagnetic material such as for example copper, and is butt Welded to the elongated portion 22, forming an enlarged section or knot 24 at the junction of these two portions. The portion 22 may be a dumet wire or other wire either partly or entirely made of ferromagnetic material. The nib portion 20 is preferably provided with serrations produced by mechanically deforming, as at 26, so that the nib 29 will be firmly anchored in the bore 14. The knot 24 limits. the travel of the leads 16a, 16b into the bore 14 so that the ferromagnetic portions 22 of the leads is prevented from entering the body of the coil form. Consequently/the ferromagnetic portion 22 are maintained for the most part in the region outside the effective range of electromagnetic influence or field of the coil, resulting in an immeasurable or substantially reduced effect on the Q of the coil depending upon the inductance value thereof. The limited insertion feature afforded by the knot 24 also serves to produce uniformity from unit to unit during production, resulting of course in more uniform Q values for a given number ofunits. sembly of FIG. 1 is then encapsulated within a suitable material 28 such as epoxy resin to protect it from the deleterious effects of the atmosphere.

FIG. 3 shows a graph which illustrates the advantages of the improved construction of the invent-ion. In this graph the abscissa represents on a log scale the inductance values of various coils or inductors and the ordinate represents their Q values. The curve A illustrates the drop in the Q values of inductors of various values as a r sult of prior construction which employ a ferromagnetic lead in which a portion of the lead was projected into the field or range of infiuence'of the inductor. From this curve it will be seen that the decrease in the Q value of the coil is very substantial. Curve B illustrates the Q values for a number of inductors made with the improved lead construction of the invention, from which it will be observed that for inductors having certain values there is no measurable electrical degradation, i.e. decrease in the Q value of the coil.

Thus the lead construction and arrangement described above provides a substantial improvement in the electrical characteristics of the inductors so manufactured. Specifically I have found that approximately of the inductors made according to this invention having inductance values between 0.1 microhenry and 180,000 microhenries have exhibited no measurable decrease in the Q of the coil when the nib portion 20 is made of a non-ferromagnetic substance, such as copper. This is particularly important in miniature inductors where size is at a premium and the designer cannot therefore aiford to increase the length of the assembly in order to prevent degradation by positioning the leads substantially outside the range of influence of the coil. For some of the coils made with prior constructions the decrease in the Q of the coil was found to be as high as approximately 26%, see FIG. 3; the Q values of such coils was found to decrease only approximately one-half of this figure when using the construction according to this invention.

While the foregoing description sets forth the principles of the invention in connection with specific apparatus, it is to be understood that the description is made only by way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. An electrical inductor assembly comprising, a core, a coil of wire wound about said core, an electrical conductor connected to one end of said coil, and another electrical conductor connected to the other end of said coil, said conductors each including a first portion of non-ferromagnetic material and a second portion of ferromagnetic material, each of said first portions extending within the eiiective range of electromagnetic influence of said coil, and substantially all of said second portions being disposed outside the effective range of electromagnetic influence of said coil.

2. The invention described in claim 1 wherein said core includes a recess at each end thereof, said first portions of said conductors being held in said recesses.

3. The invention described in claim 2 wherein said conductors each include an enlarged section at the junc- The as tion of said first and second portions, and said first portions of said leads being held by means of a snug fit in said recesses with said enlarged sections adjacent the ends of said core.

4. The invention described in claim 1 wherein said first portions of said conductors comprise copper and said econd portions of said conductors comprise durnet lead wires.

5. The invention described in claim 1, which further includes a mass of resinous material completely encapsulating said assembly to thereby isolate said assembly from the deleterious substances of the atmosphere.

6. An electrical inductor assembly comprising a coil of wire, a core of ferromagnetic material positioned within said coil, said core having an axial bore therein, a lead wire connected to one end of said coil, and another lend wvire connected to the other end of said coil, each of said lead wires having a first non-ferromagnetic por- References Cited by the Examiner UNITED STATES PATENTS 1/51 Kohring M 336-205 X 2/58 Hopkins et al 336-192 X OTHER REFERENCES Electronic Fundamentals and Applications (Ryder), published by Prentice-Hall (New York), 1953 (page 15 288 relied upon).

JOHN F. BURNS, Primary Examiner.

Claims

1. AN ELECTRICAL INDUCTOR ASSEMBLY COMPRISING, A CORE, A COIL OF WIRE WOUND ABOUT SAID CORE, AN ELECTRICAL CONDUCTOR CONNECTED TO ONE END OF SAID COIL, AND ANOTHER ELECTRICAL CONDUCTOR CONNECTED TO THE OTHER END OF SAID COIL, SAID CONDUCTORS EACH INCLUDING A FIRST PORTION OF NON-FERROMAGNETIC MATERIAL AND A SECOND PORTION OF FERROMAGNETIC MATERIAL, EACH OF SAID FIRST PORTIONS EXTENDING WITHIN THE EFFECTIVE RANGE OF ELECTROMAGNETIC INFLUENCE OF SAID COIL, AND SUBSTANTIALLY ALL OF SAID SECOND PORTIONS BEING DISPOSED OUTSIDE THE EFFECTIVE RANGE OF ELECTROMAGNETIC INFLUENCE OF SAID COIL.